My members have a custom control panel that they log into. Is there a way I can possibly set some sort of skeleton key so I can log in as those members? In some cases, the admin needs to play the role of the members (for troubleshooting, etc.). Is this possible?
I don't think there is currently an add-on that would allow "login as member" functionality from the front-end (e.g. any other place then the EE control panel)
However you could write (or commission to let write) a small plugin, based on the login_as_member() and do_login_as_member() functions. As a starting point for development see this question about Enable “Login as Member” for Additional Member Groups