If you don't need but would be fine with channeling all calls thru your fs, you could implement a mirroring filesystem. Search for mirror in the FileSystems page to get started.
If that is no option, but still want to use FUSE, you might want to look into related discussions of how to channel selected system calls via the FUSE fs and others not (read/write in this case).
That is complicated, however, and probably quite some work, so you might want to drop the FUSE approach. If you don't need to veto the removal, a file monitoring approach might be simpler.