The first internal version of GVFS was actually based on a 3rd party driver that looks a lot like FUSE. But because it is general purpose, and requires all IO to context switch from the kernel to user mode, we just couldn't make it fast enough.

Remember that our file system isn't going to be used just for git operations, but also to run builds. Once a file has been downloaded, we need to make sure that it can be read as fast as any local file would be, or dev productivity would tank.

With GvFlt, we're able to virtualize directory enumeration and first-time file reads, but after that get completely out of the way because the file becomes a normal NTFS file from that point on.

From your description it sounds like there could be usefulness in coordinating such efforts.