Another option, just for note syncing, is to remove Simplenote from the equation. Instead, make Dropbox the place you store text files, and use apps that sync directly with Dropbox. I use nvALT on the Mac and Notesy on iOS to add/edit/view text files that are synced with Dropbox. The team can still have all their notes in one place with this option, they just pick the app that works best for them.
And Dropbox’s native version control is pretty good. Go to the Dropbox site, select a file, click on More, and click on Previous Versions.