I think chess stands apart from the stupid mini games like karts and tetris because.. well.. exactly your point: It involves fighting.

It would be a cool strategic adaptation of normal gameplay.

I love the fighting mechanic of MK (that love grew in MK9). That being said I think if they find other means of exploiting the fighting gameplay of MK in side games or other formats (like chess kombat) it would only add depth.

I acutally loved Chess Kombat the most of all mini games they had throughout the whole series. I don ́t see this coming back but I sure hope it does.

Just from just that tweet i think it's grasping at straws to think that is a hint for MKX, but i really would love to see chess kombat make a return. I really wanted it in MKA just because with the huge roster the combinations of pieces would be near infinite, and the shallow movesets it would have been really suited to that kind of one-round fight with the strategy in the movement on the board.

But that didn't happen *sigh*.
It could be done in such a way to keep the dark themes and be a serious strategical side-game. I remember in MKD it wasn't exactly laughing happy fluffy bunnies.