[Suggestion, structural "piece"]

[cpaca]

Structural piece weapon: 
Structural piece objects are objects repeated many times across a base as creeper has been pushed back away from Structural Objects. 
CW3 examples would be Reactors, sometimes strafers, [based upon ore drills] bombers, and [based upon extra bases] Guppies. 
My structural piece weapon suggestion is a Planetary Heater. 
By heating up the entire planet, Creeper evaporates faster, and spores [if added] land slower due to the hotter air. 
Basically, makes evaporation stronger. Although not important on the short-term, it can work as a structural weapon while still using space, and enough [like, a LOT of them] can make a large impact on the long-term.

[planetfall]

I would also like to see a return of tech domes or similar, or energy speed/storage buildings like in CW1. The economic side of things was much more interesting in those games.