Anything wrong with: http://gdfuse.forge.ocamlcore.org/ ?
No, it worked mostly on my desktop last time I tried it (didn't seem robust vs. 500 errors from Google, and crashed a few times). However, it's not small when you include all the Ocaml libraries it depends on, so it's not an option if you want to run it from built-in flash. And cross compiling with Ocaml isn't quite straightforward, so you'll also need to maintain a build environment on ARM, MIPS or whatever you have (e.g. using QEMU).
Google Drive could maybe be useful if there existed some working FUSE implementation that would fit on cheap single board computers like the BeagleBoards and Raspberry Pi.