All Owner Approval

I would like to require that ALL OWNERS approve membership change on a group.  Is that possible (without a custom WF Activity)?

If I set the approval threshold above the number of owners on a group, the approval process never completes (because it never reaches the threshold).

I would like to facilitate this with 1 workflow applying to all groups (each with a different, & potentially changing number of owners).  I realize that I could create a WF, Set, & MPR dedicated to each number of possible owners.  Seems like a lot of overhead.

Your thoughts and/or suggestions are appreciated.

Thanks!

-Ryan