Backup will inevitably require a lot of tech support when there are Cryptowall infections, crashed servers, failed hard drives, etc. I would be sure that whomever you choose provides 24/7 tech support for the product. More than likely that means partnering with some of the larger, more well-known vendors like Carbonite, Crashplan, SOS, etc.
There should also be options for file only vs image based. A good backup service should include both a local storage option as well as an online/off-site location. Versioning is critical for being able to go back a few versions of a saved file.
In my own research, I find that it's hard to charge too much more than $5-$6 for unlimited file backup since both Carbonite and Backblaze, among others, are in that range. Image based options are more in the $15 (desktop) and $25 (Server) range with some companies charging for a license as well as the backup cost. Most third party companies seem to be using Storage Craft for image based backups.
I'd like to see a partnership with a reputable company with solid options that allows us a better price point since it will be a larger partnership than we could have by being individual partners with the same company.