MCM design would make no sense. You would go with a smaller combined size then with no issues, extra costs and performance penalties. CF/SLI on a board/card is due to lack of performance and heat. Just look on history with all the previous dual GPU boards when they came.
OK, I see what you're saying. here's my 2c.

Dual GPU cards with a CF/SLi chip between two GPUs is no better (OK...maybe a little, but for the sake of argument) than two cards in two different PCIe slots. That needs to go. Using a dual core GPU (MCM was used loosely, all I mean is the idea of two cores in one package.) seems like the way to go...natively shared memory pools, the lack of the CF/SLi chip taking up space, much more easily designed cooling solutions, etc.

Could you expand on what you're trying to say, Shintai? I'm confused and I'd like to understand exactly what you mean.