I feel like a game like this could really take advantage of Interactive Reaserch. But I feel a normal research tree (of this, to this, to this,) might not be the right way to go instead I feel a (this or this) approach would really help. Offer like 2 really powerful researches but you can only pick one and the other gets locked out. For example:
Enhanced Capacitors:
Railgun Tanks get double fire rate, with slightly reduced damage.
Or
Napalm Auto Loaders:
Railgun Tank missiles do more damage and set bugs on fire, at the cost of taking slightly longer to reload.
For Aliens:
Increased Density Carapice:
Increases all light unit damage resistance by 30% but slightly decreases speed.
Or
Decreased Body Mass:
Lowers the weight of all light units greatly increasing speed at the cost of decreased health pools.