When you finally get to some system where you can put a bunch of squads into a battlegroup (a really needed feature to allow us to not have to individually select squads when we want to replace a whole group with another group of BR squads), allow the Create game to select the army AND any tier (or all tiers) from your selected battlegroups to fill in any open holes.
This way you can setup say T4 to T4 match without having the non-player roles filled with T1-T2-T3-T5 stuff (unless you set it up that way).
Also fix the AI to fill the open slots with the type of army(s) selected for that side. For example, Bre West with Soviet and German. Players can be Soviet, but AI fills with American.