As I'm not yet experienced enough to speak intelligently on questions 1 and 3, I'm only going to adress question 2.
 
The only race I'd like to see added to the game are Tyranids.
 - I'm make their game pieces purple.
 - I'd give them a massive pool of tier 0 troops, with plenty of ways to get them into play fast and cheap.
 - I'd give them a very limited pool of tiers 1+.
 - I'd have combat cards key on higher-tier troops to grant bonuses to tier 0 troops to reflect synposis.
 - I'd give them ways to easily generate tons and tons of reinforcement tokens.
 - With so many ways to generate cheap or free tier 0 troops and reinforcment tokens, I'd consider having them be automatically destroyed if routed.
 - I'd consider giving them an alterante win condition (such as take over any four planets containing an opponet's buildings) if it could at all be balanced.

As I'm not yet experienced enough to speak intelligently on questions 1 and 3, I'm only going to adress question 2.
 
The only race I'd like to see added to the game are Tyranids.
 - I'm make their game pieces purple.
 - I'd give them a massive pool of tier 0 troops, with plenty of ways to get them into play fast and cheap.
 - I'd give them a very limited pool of tiers 1+.
 - I'd have combat cards key on higher-tier troops to grant bonuses to tier 0 troops to reflect synposis.
 - I'd give them ways to easily generate tons and tons of reinforcement tokens.
 - With so many ways to generate cheap or free tier 0 troops and reinforcment tokens, I'd consider having them be automatically destroyed if routed.
 - I'd consider giving them an alterante win condition (such as take over any four planets containing an opponet's buildings) if it could at all be balanced.

As I'm not yet experienced enough to speak intelligently on questions 1 and 3, I'm only going to adress question 2.
 
The only race I'd like to see added to the game are Tyranids.
 - I'm make their game pieces purple.
 - I'd give them a massive pool of tier 0 troops, with plenty of ways to get them into play fast and cheap.
 - I'd give them a very limited pool of tiers 1+.
 - I'd have combat cards key on higher-tier troops to grant bonuses to tier 0 troops to reflect synposis.
 - I'd give them ways to easily generate tons and tons of reinforcement tokens.
 - With so many ways to generate cheap or free tier 0 troops and reinforcment tokens, I'd consider having them be automatically destroyed if routed.
 - I'd consider giving them an alterante win condition (such as take over any four planets containing an opponet's buildings) if it could at all be balanced.