It makes sense, to me at least.
Also from a collecting standpoint, I think even a good set of Generics or Generics by side can be desirable. It was rather novel for example in 1941 how the sets were done, because many people have uses for certain units in certain colors which might not come standard in other national sets. For special forces units, or a lend lease feel, or to include minor nations somewhere. In the same way that some people enjoy getting their hands on Lime Green Brits, or the nice cool Grey germans from Revised, because they have a color scheme that works for whatever purpose; similarly, the units from 1941, because they are generics, could potentially be included in other scenarios. Basically 41 gives you an incentive to pick it up just to grab a few of those special units for the arsenal in a nice color spread. The Japanese Tigers for example, or the nice Warhawks.
What you are discussing with ships is exactly on point. The sort of confusion that arises between cruisers destroyers and the like, because of the shapes/sizes used by different nations for the same basic type. I think you could do a lot just with size on the length dimension.
If for example all destroyers were exactly the same length, and there was a reasonable spread between the length of the types. For example, start with the cheapest combat capable units and develop some exact ratio that is consistent for all nations.
So, using normal A&A size units, maybe something like…
Subs are 1 inch
Destroyers 1 inch and a third
Cruisers 1 inch and two thirds
Carriers 2 inches
Battleships 2 inches, since its fairly easy to distinguish between the carrier and battleship by shape.
So the sub is the baseline (whatever its length is determined to be) and all other warships build off that.
Sub x 1, x 1.333, x 1.666, x 2 etc to keep it all visually simple and immediately recognizable.
Or in the case of micro, you could make the base sub length smaller by 25% or 33% or whatever seems to make it feel visibly more micro, when compared with the normal scale A&A. With the ships listed above, plugged into set length ratios by type, I think it would be pretty easy to tell them apart, whether generic or national in shape. I do agree, squared vs rounded is very important for differentiation of units (more than width in many cases) so I would try to use that to differentiate if I could. Likewise height features also help to differentiate units provided they are markedly different.
That just leaves you with the Transport unit, which should be generic for all players, and (critically!) should be able to “seat” any land unit capable of being transported. In other words the ship should break relative scale to be more in line with the land units it transports rather than other ships. Because this requires a flat topped transport (no smoke stacks!) I would suggest a very different visual shape from the carrier deck. So elliptical transports and squared carriers for example. The transport should likewise have a well balanced and flat bottom so that it “slides” easily with units aboard, or stacks well atop a chip in the case of large unloaded transport stacks. The Transport unit is highly abstract to begin with, and so I think its sculpt should be more functional rather than decorative.
Carriers, Transports, or any unit on which another unit can can be loaded or “parked”, should have a good center of gravity, flat bottom, and no wobble. Likewise, any unit which can rest on other units should have a good center of gravity and a flat bottom to minimize wobble while atop the other unit.
It would be nice for example if units like Mech, or Artillery were designed to sit more snugly on top, or alongside of units they are paired with. I think micro has the potential to do this, and provides a nice opportunity, since you’d have smaller infantry and fighters etc, but by introducing a really strong relative scale by ship type, you could still have pretty large Carriers and Transports. I think that with Tanks, as long as they were paired exactly by size, you could probably find a nice way to scale it using Nationals. But I do agree that if you wanted to do generic by side, the models knp mentioned sound pretty solid to me. I think I’d be happy with those.
The only unit that seems to really call out for Nationals is infantry, but this also has to do with how large the infantry currently are. At a smaller size helmet differentiation becomes a little less significant, and that is the main distinguishing characteristic of infantry. If you did do generic by side even for infantry, I think I would more readily accept German helmets on the Japanese, than I would all the same helmets for the Allies. You have to go down pretty small before the differences become negligible, I’d say something along the lines of the 40th anniversary Risk units, before people wouldn’t be all sad that the Brits and Americans and Russians look too similar with their helmets.