I've searched but i didn't find anything so take this as a suggestion.

Basically one could make the bots use one weapon more than another, for example if you have a rilfe, smg and mg for a ww1 configuration, you'd make the mayority of bots use the rifle and the minority use either the smg or the mg, so that you don't see whole squads using mgs.

I don't know how to mod so maybe it's not possible, but that would be the basic idea.