Text editor needs a lot to be local, because you're doing a lot with large blocks of memory, and responsiveness is critical. I like the idea about the save point being remote.

Like sharepoint, but without the destroy-file-on-save feature it triggers when you save against it in gvim in some circumstances. Doing it via git integration could be a great way to achieve this without rebuilding the world.

Could be achieved via a FUSE filesystem wrapper on linux workstations.