As for cavalry and bicycle troops - I don't necessarily see them as an issue (since in WWII you saw them exclusively fighting dismounted), but it would be nice to add a distinct class of transports into the game that are not APCs/IFVs and are therefore unarmored (and often unarmed). Trucks, motorcycles, and yes, even horses and bikes could go under that. Technically you can already have those, but the AI tends to handle them the same way as APCs, which is not always ideal...
However, there's even a way to handle unusual units - simply set their auto-purchase to 0. This means that for any generated scenarios, the AI will never "buy" them, and won't have to be confused by then (unless you make it ).
Otherwise, I think Ardennes '44 is a great mod idea
Well the issue I have isn't with combat, but with transport, and to a lesser extent, aesthetics. Right now there's no way to my knowledge to have dismounted, unmanned transports, they are always mobile and considered manned by someone. So while in reality the cavalry/bicycle troops would be dismounted and their bicycles and horses hidden, their transport is still considered manned and susceptible to movement orders and attack in the event it is discovered. The aesthetic issue is that there's no sprite representation for dismounted transport, which is an issue for open topped transports as well. So even though the horses and bicycles would have no one on them, the sprite will always show them as being mounted. It's a small issue because the GUI can let you know if transports are mounted/dismounted, but one that bugs me at least lol.