Difficult: the Google API doesn't seem to support random access to files, only whole downloads. So you'd need a caching layer to buffer any changes, prefetch, etc...
And even then, it would be catastrophically slow for true random access. Note that even Dropbox isn't implemented with FUSE; it just watches your ~/Dropbox folder with (presumably) inotify.
Both Dropbox and Google Drive keep a local copy of all your files unless you explicitly tell them to sync selectively. Your local filesystem is the cache, so there is no need for random access to remote files. FUSE would be not only slow but also completely unnecessary for this use case. inotify is exactly the right tool for the job.
And even then, it would be catastrophically slow for true random access. Note that even Dropbox isn't implemented with FUSE; it just watches your ~/Dropbox folder with (presumably) inotify.