Main issue is this would be yet another project fully based on volunteer work. And one of a very big scale.
This thread is a wishlist for an open source project without developers
imo a higher priority is creating a 6v6 vscript layer for maps. custom minute round timer, pregame DM, etc can be implemented into the maps themselves. Instead of relying on plug-ins which will need updating as the game updates (which this update perfectly demonstrated by happening in the middle of EU scrims)
Using vscript, we can already add entirely new mechanics. Weapon balancing, bug fixes, new mechanics, etc are already possible in TF2 with this. And if a promod ever exists later on, we'd have these vscript maps ready to port over