When you do get around to working on this, please don't tie it to any specific "cloud sync" implementation, especially not Google, iCloud, or Dropbox (or any other service where your "cloud" files are readable by employees of whoever runs the service.)
There are several methods out there which synchronize directories between computers -- Dropbox is probably the most well-known example, but Google, iCloud, SpiderOak, Resilio Sync (formerly BitTorrent Sync), Keybase, and several other products all perform the same function, with varying security scenarios (i.e. Dropbox, Apple, and Google employees can read your files in their respective "clouds", SpiderOak and Keybase encrypt the files before uploading so they cannot be read by their employees, and with Resilio there *is* no central server from which files could be read in the first place - just other peers.)
For all of these products, it should be possible to configure each client with an absolute filename which happens to be within a sync'ed directory, and gain the automatic "sync the file between machines" functionality. I'm doing it right now by manually exporting and importing a "memory_export.bin" file to/from my Keybase private directory. To me, the only thing which is missing is having MooltiApp automatically export the file after a change is made, or import the file if its timestamp happens to be newer than the last timestamp it was aware of. (Of course this assumes that the sync mechanism also synchronizes timestamps, and that the peers all have accurate clocks.)