I like the idea of an outpost building with a small amount of territory, also the weak phase 2 ram. I also kinda wish there were some champion units and fortresses in phase 2, but maybe that's too much.

Are mercenaries worth using? I feel like they cost too much metal to be worth it; that needs to be saved for champions. 

I use it regularly. I've changed hotkeys so z is select idle, x is select wounded, c is call to arms, and v is capture building. All my favorite hotkeys there on the bottom left of the keyboard.

only one I found that is CC0 and at least has some similarity with Nike is this one: https://open.smk.dk/en/artwork/image/KAS1604?q=*&page=5&filters=has_3d_file%3Atrue

Would it be possible to make it so buildings can only be captured if they are half damaged or more? I think that would be good for gameplay. I avoid building towers now in multiplayer because it's too easy for enemies to capture them and too hard to get them back.