This basically boils down to:
- identify wikis with a local VE feedback page (it may be that the wikidata list is not enough for this);
- determine which ones may benefit more from centralization (hint: very low traffic, completely unmaintained pages qualify);
- announce transition will happen - give a deadline (not just on the feedback page itself, of course);
- identify helpful volunteers at the other wikis, who are willing to take care of their feedback page, so that they can keep it instead (archiving old threads, getting rid of OT posts regularly, helping to put feedback in an actionable form and to report it on Phabricator or on the mediawiki page).