A wider range of chassis would be very good.
I remember a certain game... EARTH 2150. Even though it is a fighting and collecting limited resources game, you had to research stuff to progress. You could research up to 6-7 types of chassis and attach weapons in certain ways and combining them in any way you like. (you could strap on a Plasma cannon and a small rocket launcher on the same unit. Every chassis could have a certain type of shield attached. Shields would block energy weapons until depleted.
So, what I though would be nice to see in OP3. More chassis types. Add the shields thing. It would be interesting to see a Thor's hammer Tiger beaten by a microwave panther, just because it had enough shields to give it enough time to kill it, whereas a Rail Gun would shoot straight in it, ignoring any shields. Shields could help against EMP also... if a unit has enough shields, it could block one EMP hit.
The intermixing of weapons on one chassis is really cool, but we can live without it just fine.
Also, something I didn't see quite right about OP2. If your CC gets blown, then you are paralised... If I had the technology, I would make all my buildings able to run independently.Maybe if your CC gets blown, you buildings still function, but at a reduced productivity (half?) That way, you would need to take out both the CC and the SF, to completely paralise someone. If I would run a colony, I would think of away to ensure my colonies survival by keeping a possibility of rebuilding my CC if it was destroyed. Also, maybe if you had a Smelter (and a CC) still alive (and connected), you could slowly build a SF kit to rebuild your SF if it got destroyed. That would require an empty ConVec to sit next to the Smelter during the whole building process. You Smelter would run at 70% efficiency while your SF is being rebuilt.
meh... idea spillage