As I don't have the ruleset and only have played one game, I can't really say that much about composition.
However I do believe that the missions are there to help balance out the game, as you can make quite dull forces that may be nigh on unkillable (all heavy armour and rapid firing heavy weapons), but would loose all objective missions to a teleporting freak show.
The game i played was wery enjoyable and I see great potential in AE:Bounty.
/Jaeger