As much as I would like to see it this runs the risk of raising a few issues we don't need in AH. It would be great for specific scenarios, but really the Bismarck was out of action before it really had an effect at all on the war, and aside from that specific ship types don't matter. A generic carrier is as good as anything except for historical reenactments. Submarines would be a much more effective addition.
The Bismark isn't on the top of my list for a reason. But it would make for a fun one-shot (this day?) event (Sink the BISMARK!). The two BB TF in the MA was an afterthought, as well.
Submarines would be coding a completely new game which, unfortunately, is already in existence. Sub sims are, by nature, long patrol simulations (with time compression between encounters). AH doesn't lend itself to such. AH is more of a constant action format. Heck, players complain about flight time to action as it is. There is no time compression in AH, there's only reduced scale. The only way I can see submarines in AH would be as AI. Still, even making them run patrols to intercept task forces would add little to the game other than making players angry that a task force was hit by an AI sub instead of at least becoming a surface ship on surface ship action. And if it wasn't AI? It would merely be 'fleet camping.'
Which .... brings us back to offering more options in surface fleet vs surface fleet. Saying 'generic ships are good enough' is kinda like saying 'generic tanks are good enough' or 'generic planes are good enough' (the carrier in AH isn't really generic, nor is the cruiser, iirc, one is based on the Essex class and the other on the Baltimore class, I believe). Besides, wouldn't it depend on individual perspective when it comes to what's 'good enough' (I'd settle for the first ship on the list, not generic).