Perhaps an easier solution is just to have a folder in the FSU SVN called compatibility and when you select the outdated stuff to delete, you hit move instead targeting the compatibility folder, you dont even have to organise it the folder, just post it as an asset dump when you post the new version of MVP then someone else in the community can organise it even if you guys dont want to, I know I don't have a problem with doing that as it would only take a couple of minutes to do, plus a few more to test and VP the files.
Once you have posted the dump file, clear out the compatibility folder and start again, this way your SVN dont get clogged up with masses of redundant data, just the difference between the last release and the current WIP. go thought the same update process again, then when you release again you replace the dump file with the new one and someone like me will add that to the old compatibility pack and release the new version.
For a the cost of a few seconds per update you get to keep the MVP shiny and new, while the guys who want to play older mods get to keep playing them with the improved on retail content, all the while guaranteeing compatibility is someone else's problem because you are not producing the compatibility pack.
Still, a "compatibility package" would be a better idea than keeping an entire set of old VPs, which serve no purpose other than clog up the disk space. Something like the outtakes pack, also containing tables and scripts from the old core. It would disable all new 3.6.14 features, essentially making the new VPs work like the old ones. Just drop it into the old mod folder and the mod should work, benefiting from all the cosmetic improvements that were made for the new VPs.
Please, go ahead and make one. And then debug it. And then take care of the people who use it wrongly. Have fun.
How is that different to any other mod? Look If you want to create a septate project board for it so mods and admins can divert compatibility mod related issues, I will happily take the flack from newbies and the incompetent. I know I am a glutton for punishment but I Also like a good challenge (queue comments from veterans like The_E along the lines of you dont know what you are getting into) and I am prepared to take it on.
Perhaps the FSCRP could help with this sort of compatibility stuff?
That's a big ask for a team with a heavy workload as it is