DavecUK It makes me wonder if it's actually worth shutting down all external server access to forums until all databases have completed, it might well be faster that way? A simple message of forums being updated would suffice to inform users.
Currently, there's no system to automatically do that for every forum. When the new update rolls out for FreeFlarum, all forums will be instantly turned into a maintenance mode (in Flarum config), so that everything goes smoothly during major upgrades.
DavecUK As for disabling extensions, I've a suspicion think certain ones need purging before disabling as well
It could be possible to rollback migrations for every forum for that extension. But I am not sure whether that would actually be needed. Should the extension be re-added in the future, forum owners will need to re-configure it (although that doesn't to be too big of a hassle). So, I could create a script that rolls back the migrations when it's needed, not on every uninstall - a nice compromise, I think