Create some sort of Special:ConvertCollaborationPageToWikitext to revert creation of a CollaborationHub.
- input page title, change content model and replace with output wikitext of basically the same thing, sans silly styles/boxen/whatever
- subpages remain subpages, but with partial transclusions replaced with links (or maybe just output that too?)
- also convert subpage collaborationlists to wikitext? Maybe have this be an optional (set of) checkboxes, listing all such pages
- creates new revision as wikitext; does not touch existing revisions, or content models; assumed general script will be used for that if needed per T192326
Note that this should later be interoperable with the handler for creating CollaborationHubs by converting from existing wikiprojects in-place (T135408). Or something.