My main goal would be to downgrade the XML version as much as possible. So identify the data which data would be lost and choosing what can be safely discarded. (Maybe along similar lines to the strategic Note markdown trimmer that @kku did in SuperTool.)
The thought is that more people would be willing to share data in Gramps .xml if it was easier to assure broad useabilty.
So a county’s Historical Society might willing to maintain a Place database (or maybe just cemeteries list), local history reference book list, or local person list on an instance of @DavidMStraub 's Gramps Web. And visitors could pick and choose items to Export/Sync to their local Gramps.
But it wouldn’t fly if everyone had to be on the highest release of Gramps all the time. That would be as aggravating as Microsoft constantly pushing upgrades before you can do a particular task.