I'm not trying to make it realistic though, and I'm not trying to turn xbows into a support weapon - it could be used in such fashion, but a player who decides to stick with xbows shouldn't be fucked. That's my point.
Why are you so adamant in making crossbow a main weapon, so to speak? Historically, it WAS support one... unless you go for HL-like crossbows, that are reloaded like a rifle, have a clip and yet shoot powerfully enough to kill.
Why do you want to add a weapon to the game, which will surely go against all logic? Aren’t there are a lot of other ones?
Next, you'd like to add thrown rocks and what, you will balance them so they will be on par with bows and crossbows? In case someone would like to play using only rocks? Or make knifes ultimate weapons of destruction, on par with two-handed swords? Why two-handed swords were invented, if knives rule so much, then? (And require much less strength from the user, too.)
Different weapons are made for different purposes, and some were never intended to be ‘primary’ or even ‘balanced’.
And about 'cosmetic differences' again:
Only 1 ap more to shoot, that's laughable! And 'a bit' more powerful, no doubt. And with same skill requirements, right? No? Then the situation will be unbalanced towards crossbows, then.
Btw, about ‘fast first shot’... I agree. But it would be viable only in RT or SPM. In TB, it doesn’t matter. Who gets the first move will fire first - no matter how slow weapon he has. To a question of limitations of TB again - only ‘shots per turn’ are important... no to mention that ‘disrupting your current action’ in unheard of in TB. (Unless you mean continuous actions like running, and interrupts... but there are no interrupts in Fallout. Will the be in AoD?)
Insta-kill weapons are boring, so I shall repeat: where is fun in that?
Well, I pretty much enjoyed playing Fallout with a gauss rifle, and shooting people in the eyes (Sniper and better criticals perks taken).
Now that is almost instant-kill weapon... and lots of fun.
Your idea of fun is MMORPGs, where you have to chew on a monster for an hour? Thanks, I'll pass.
Anyway, that’s your game, and you can do whatever perversion comes to your mind with it.
But you asked for my opinion and suggestions - here, you have one. *shrugs*
But I still don’t understand why you want to balance every available weapon to be used as a ‘primary’ one.