"Must allow changing git repository, code review, and ticketing systems from Gerrit and Phabricator."
I worry a bit that requiring the solution to support other repo/CR systems will give us a worse result. I'd like to see much tighter integration with Gerrit, like inline comments and uploading new patches, etc. (as explained in my wishlist). I think overall solutions that are more tightly integrated will provide a better user experience than ones that are more abstract and provide general interfaces.