I'd like to see a abstract front-end that can work with any version control system, including a stub like that.

Someone pointed you to that existing thing already; I looked at it, and it's read-only and pretty specific for looking at history rather than manipulating the files (check in and out). I'm interested in checking out files when a script modifies one that's under control. I just redid a script from Continuus to SourceSafe, and have also used PVCS here, and ClearCase is in the wind.