Holy hell! Love those tanks! Looks quite ixian to be honest.
I wonder about how hard is to make new sprites. I made those static buildings and mix-and-match were damned. I am not sure I used the proper whit-grey colours what the game (theoretically) swap to faction colours... Maybe +3-5 frames per buildings could work ingame, not sure. I usually just tinkering around but rarely implement anything in games myself.
I once made some unit sprites for someone. Have no clue if he may succeed to insert them ingame or not. I may still have those sprites somewhere if anyone interested (doubt so?)...
What I wonder since a while is... Well, I saw tons of new units in the different scenarios like AA-tanks (legion gatling or what), RPG quad, flametank... I would love some scenario what let the player build or access via Starport for all those new units! I could imagine some nice assault groups with them.