A cartridge version with cut scenes, more graphics, multi SID support, story, more units, multiplayer etc. would be an option, it this genre should resonate with a big enough C64 crowd
This is just screaming for it, because there is nothing like this on the C64. Absolutely nothing. And to have such a good one, coming from you now, is breathtaking to me! I'd love any kind of expansion or player made maps, yes. The very first thing I would probably suggest is, using graphics tiles for everything, nothing super fancy, just so it's a bit more easy to read. No idea what cut scenes you were having in mind. Multiplayer is a biggie. I'll drumroll for this! I'd get this boxed. I'd love a floppy version too! It doesn't have to be a one-loader ... being able to save and load maps could open up a kingdom for map making.
The city idea I was thinking of, is taken from Famicom Wars/Advance Wars, I'll admit. But generally -- buildings with a function, or other stationary objects, airport, seaport, ships, subs, ah don't mind me ... Sorry to throw so much at you all at once. I'm just so happy! Lots of love!