Alex,
So sorry for not getting back to this sooner.. I'm sure you were thinking I missed it after a month..
Anyways, wanted to let you know your request was received and we've added an issue to investigate it. One thing we do want to do, that should have a similar effect, is to let you set the redirection either in the SCLogin module or a per-button instance basis. Then, the returning redirection in JFBConnect would work for auto-login and the buttons could have their own redirection. The new user redirection in JFBConnect would remain as a site-wide settings as well.
Hope that makes sense. We'd love your feedback. I can see this being something in the 5.1 release (March/April'ish).
Thanks,
Alex