Which brings up another question -- how much C11 do you expect to get out of MSVC? The situation has improved, and is still improving, but to this point in time even C99 compatibility is far from bulletproof.
It's mostly a hope at this point. I'm still planning the project, haven't started coding it yet. And I do most of my development on Linux, but will build on MSVC when it's far enough along to get other people to test it. So my hope is that C11 support will have improved some by then.
If it hasn't, then there's always MinGW, but I'm trying not to rule out MSVC at this stage.