About porting the 3dgs runtime to Xbox. Xbox uses DX 8.1 . Almost all functions from the DX 8.1 SDK is in the Xbox XDK. Porting a DX 8 / 8.1 game to Xbox is not that much work as many think, all that has to be considered is hardware limitations. Since A6 6.2 use DX8 that would be the best bet for Xbox.
But to be honest I seriously doubt that a xbox 3dgs runtime will ever be made.

And if any of you wonder. Yes I have tried the Xbox XDK