It's great that you managed to get cron working the way you wanted. However, I'm curious, why not just put your Vim settings on Dropbox or something like BitTorrentSync - then alias your local settings/configs on each machine to the corresponding file/folder in your Dropbox?
I use this method for all settings and configs that I wish to share across multiple machines. Personally I find it more manageable than any other solution, and certainly less convoluted than "multiple rounds of ssh duncan@some-server... git pull origin master".
I've been with SDF for years. I cut my Unix teeth on their servers. They're a fantastic host and I am very impressed that their "Meta Array" coped with the influx of HN traffic without skipping a beat. I've been periodically checking the site, with an empty cache, while this link was on the HN front page and page delivery was consistently sub-1s. Theirs is extremely cheap hosting too. I have nothing but praise for the SDF.
"this cannot be done programmatically" - are you sure about that? I think any half-decent programmer would be able to do this programmatically. A simple logic condition (if-then-else) should cover it.