I also think Blitzkrieg is a potentially confusing term, and prefer Combined Arms to describe these relationships. To me Blitzkrieg is a very particular kind of (German) military doctrine, which uses combined arms and a strategy of continuous advance, likely with units on hella meth to get the job done quicky and on no sleep. Sure the other belligerents saw the advantages of lightning war over the slog of the previous world war, and adapted, but I think it has quintessentially German connotations. Such that Americans or British troops having a Blitzkrieg ability seems kinda off. 'Blitz' on the other hand is a more general purpose term, like even in American Football we have such a thing as a Blitz, where the defenders all rush the line to try and sack the Quarterback. Or adding the definite article "The Blitz" I just think of civilians holed up in the Underground, waiting for the air raid sirens to stop. It's a bit of a mixed bag for a term hehe, but in A&A "Blitz" is a technical descriptor for a particular kind of attack movement, specifically for the tanks which move across 2 spaces.
For the thing about Fighter aircraft not being able to hit infantry unless there are combined arms in the mix, this makes a certain sense. Like I can imagine well trained Infantry units scattering and heading for the tree lines, but also, every WW2 movie I've ever seen has that shot with a Fighter flying low to strafe a column of Infantry units. Like that shot is in ever flick pretty much. For my part I think if one wanted to include this idea that infantry would have an easier time hiding than say a heavy ass tank that weighs several tons and can't hit the floor like soldiers might, that this could maybe be achieved by focusing only on Elites. In other words Conscripts and reg Infantry could be killed by the fighters, but the Elites are maybe dodging under the treelines - the columns all camouflaged up with nets and decoys. Like you'd still end up with some weird stalemate situations there probably, but it wouldn't make the primary fodder unit for most nations un-hittable by the primary air unit. For me that's more of a practical mechanical consideration, since right now I struggle to justify air purchases over other units which provide a more reliable hitpoint, or more consistent attack/defense power.
There are niche instances where it makes sense to buy fighters, say if the territory is already at the cap, or where you can overwhelm a player that doesn't have sufficient production capacity to spam fodder units. For example Japan can smoke China pretty easily with massed air provided they use their Air HQ as well for the bonus, using a tactic I call the Air Blitz (another kind to the whole use of Blitz for everything hehe) but basically that's a situation where naked Air keep attack to kill ground that are unlikley/unable to hit back, which is something that can be done to pretty good effect here, though again it's a bit asymmetrical by Nation.
For combined arms with the Tactical Bombers, one issue there for pairing multiple unit types is whether/how the player can determine which unit will actually get assigned the bonus. For example in A&A all the units effected just Hit at 3s so it's easy to see how a bonus to one or the other might not really matter if multiple unit types are capable of receiving the bonus. But if some units have targeting, or have different hits at values, then it's a consideration. Like it might make more sense to assign the bonus to an Anti Tank unit with a chance to hit at a higher value, or with an opening strike type action, as opposed to say some other unit type that can't do that stuff. I think for order of battle type things it'd difficult because the battle screen moves so quickly and it's hard to tell which units are being effected by other units.
Also when each nation has different unit types available, having all these very specific targeting actions means that players not only have to be familiar with their own unit roster, but also all the opponents unit rosters, in order to fully appreciate what's going on. So for example if Allies have one type of ship the Destroyer, but Japan has a supped up version of the same, the player needs to understand how both work before they can make a considered attack plan. That information is hard to parse in advance, or from tables. It's even hard to tell from fighting actual battles if you're only seeing one side of the equation. The player really almost needs to have a purchase menu and go through the motions with each nation to grasp what's going on in it's totality.
One possibility would be to show a complete purchase screen that shows all available unit types (including tech advance stuff, or stuff specific to only certain nations) but to have the units blanked out if not available. So for example if there is such a thing as a super sub on the board, that the player can quickly see the TUV attack/defense or bring it into the calc and get the quick read. But then the purchase screen would basically just be the unit notes all over again, and probably too much information. If the idea is for the player to control an entire team, it's more likely that they'll see the little differences, but if they only control a single nation, you could get the same sorta thing for teammates, where the player just doesn't really know what makes one ship type different for some nations. HQs are like this in the opening rounds of the game. If you are playing as a power that has them you can see what's going on, if not, it can be very confusing to understand how they work. I learn by using the stuff, so the only way to really figure it out was to just keep playing different Nations until it started to click, but it's hard to cross ref or use the experience of one player nation to inform how stuff is going to work for another. For examaple switching from Germany or Japan which have HQs on their first turn, to USSR or USA which don't have them. Probably the HQs need like a whole page in the manual just to themselves. My shorthand is basically without HQs I'm probably going to lose whatever battle, so a lot of the early game is just delaying/stalling tactics till them come online. Or if Axis to race early and make the most of them before Allies catch up. A Nation like Anzac isn't even really functional until they get their roster expansion, so it's also hard to compare the larger nations on either team to the smaller ones on team Allies.
For manual drafting advice, I'd say M3 off the factories and M3 in the water for Cruisers and Destroyers would be worth highlighting. It took me a long time just to figure out why I was able to move some units so far, and others not far enough hehe. The terrain for M2 units basically. I still think it's hard to parse movement changes like that, and think it would be somewhat simpler if terrain didn't effect movement at all, but only attack/def power. Right now a lot of terrain features feel too similar in terms their effects to me. Forest and Mountain and Urban I guess, since those are the most common and the descriptions have very a similar read. I think Urban to me suggests that it would be easier to move armored units rather than more difficult, but I also just have a hard time envisioning such huge regions as particularly urban. Like I guess if everything is all bombed out and bridges and roads are destroyed it makes sense that it's hard to get around, say Stalingrad where everyone is fighting in rubble, but then I also think of it more like the roads still being in alright repair. Or where there are population centers capable of rebuilding the stuff and roads that don't flood out or freeze for half the year. Or some desert stretch where sand grinds the gears. For me movement adjustments are the most challenging to get the head around, because often I can't really tell until I try to move something that the movement won't work. Trying to parse the unit caps is similar, but there's more give there at 10 units, where a terrain -1 movement might be more of a surprise, and all or nothing for maneuvering stacks with the tank tow. That said, I think the movement stuff from Rail is the single best thing this game has going, since that stuff really changes the emergent playpatterns and the ability for players/AI to clap back across a pretty good distance, in ways that keep me on my toes. The m3 movement I think creates a nice push/pull dynamic, and makes logistics just foggy enough that I'm always second guessing whether I can actually hold vs enemy counter attacks on the follow up turn. I love that stuff!
Anyway, just more rambles, not sure how useful my impressions are really, cause I've been at a while so I'm probably too familiar to see the forest from the tress for some stuff, but I can remember having some issues with the learning curve in those areas.
Nice work all! Keep it hummin'
ps. here's another solo start to J3. Similar thrust but going after the Pacific Allies instead of the Brits in India. I just bought a couple extra minor factories to shore things up and set big wall down in the south Pacific with the fleet. Felt pretty solid. I had like one big TUV trade vs China but I think they're about spent now. Brits gave me some trouble and almost took Bangkok after we whiffed in Lower Burma, but all and all pretty smooth sailing. Flexing against the Allies with the Japanese fleet I'm not sure there's anything Anzac or USA could do to threaten an approach, or an attack that wouldn't have them getting wiped by a secondary fleet, so they just sorta break and run away.