Making mass changes to users based on secondary usergroups?

[abjds.com]

My short question is -- is there any way to mass-move or otherwise mass-alter users based on the secondary usergroups that they belong to?

I've looked around in both 'Move Users' and 'Promotions', but both of these only list users or make changes to users based on their primary user group, which doesn't help me.

Basically, we have several publicly joinable usergroups (set up as secondary usergroups) which allow our users to access various different parts of the forum when they join them. They are all secondary so that our users can choose to join more than one without affecting their basic forum usage. However due to lack of activity in some of them, we'd like to "merge" them into other, more active usergroups.

Since I can't find any nice simple "merge usergroups" option (and if there is one, thwap me and point me towards it!) I figured a mass-move of the users from the inactive usergroups to the active usergroups was my next best choice... but I simple can't find anything which allows me to select them all based off the secondary usergroups. :/ Everything seems to run off primary usergroups only.

Is there any way at all to do this, or any mod that I've overlooked that might help me? Or is my only choice going to be to alter someone else's mod to better suit my needs? (I'd prefer not to if I can avoid it -- I'm just a hack when it comes to backend stuff... but I don't consider the idea of manually editing hundreds of user accounts as a viable alternative.)

Thanks in advance for any advice!