First of all, I understand that it’s probably not feasible to allow customisation of the bot weapon loadouts, and possibly classes as well (although they don’t seem to make use of perks at all), for balance reasons. That said, why not allow us to customise their appearance, i.e. weapon shaders, outfits, headgear, etc?
Four slots could be added below the current 12 loadouts, labelled ALPHA, BRAVO, CHARLIE, & DELTA, with only the permitted cosmetic details customisable. For matches with two or three fireteam players the remaining bots could either be drawn randomly from each player, or follow the customisation of whoever is playing ALPHA (just to keep things simple).