What would Chess be like if it was a resource-building game like StarCraft?
Managing economic flows, improving tech-trees, these raise StarCraft above mere "strategy" games like Chess (where you start with fixed resources and cannot increase the size of your army) because they more closely correspond with how real economies actually work. They are better simulators for reality, better teaching tools. Chess is really a "tactics" game, come to think of it.
So how would Chess be turned into a strategic resource builder? We want to keep as many of the usual rules of chess, and make the smallest number of changes.
Well, you'd start with a mostly empty board instead of a full one. The logical minimum would be to start with kings. (Although a couple of pawns might be handy as well)
Here's the first rule: Each "move", you can either move a chess piece as normal, or have your king (command center) generate a pawn (SCV/drone/zergling) into any empty square next to the king. A bit like transfer chess.
The king is the only piece with this ability, logically making it the most important piece on the board. We will now add one more rule: Your pawns can also "take" your own pieces (in the normal diagonal way) and in doing so "upgrade" them to the next most powerful piece. (Similar to 'queening')
Let's set the "tech-tree" order as:
If you're playing this on a real board, you'll be "capped" by the usual number of pieces you have. Alas, no multiple queens or kings.
So, this is black moving normally, (making a rush?) but white doing an "upgrade" of one pawn with another. Like most resource builders, the start of the game is pretty slow.
And that's all. The game then proceeds, with each side spawning new pawns from their king, upgrading units, and deploying them against the opposing side.
As for the victory conditions, I think keeping "checkmate" is fine. Although in StarCraft it's possible to fight on without a command center, we can probably assume that wouldn't be the situation in ChessCraft unless you were on the ropes anyway.
I haven't actually played this against a person yet. But now I want to.