I keep saying this- but Stardock has the tools needed to make such a game using Legendary Heroes's units/items/world (or a variation thereof)- many things go one for one with Kohan, and you've got a bunch of heroes already designed.
With Ashes engine and multithreaded AI, you could have larger armies than what Kohan had, and avoid some of the townstealing exploits that Kohan had with an UI that could adapt to human cheese.
If you put the game out there flat out as both a spiritual successor to Kohan and "an accessible RTS game without peon management or excessive micromanagement", I could see it doing well. I'd also advertise it a bit to the MOBA crowd as an alternative game for them to try. I see Kohan as sorta an ancestor to MOBAs in general as well.
In terms of keeping the community going, it has to have the addictive people want to keep playing it factor. Going F2P is an option. Have a founder's option that gets new content first, and make your money off of cosmetics. (you might need to go the fanservice route some)
(Allow F2P folks to ban content they aren't going to get yet to avoid crying though)