limited soldier-type slots
as of #102 (closed)/#125 (closed), all soldier-types you've bought queens for will spawn in combat. As we add more soldier-types, that's not going to be acceptable: we need a way to choose only a few you'll be fighting with. design + implement some system to do this.
wouldn't hurt to get rid of "[soldier]-queen" as a unit when designing this, I think. too much overlap with drone-queens, and queens don't really participate in combat - the lair spawns all your stuff.