Facebook redirect controlled by URL parameter

I have a feature request for the Ultimate Facebook plugin.

I can setup the login to redirect to a backend url or a site url after facebook login, but I need it to be able to redirect to a url determined by a parameter

On my site, the login page has a parameter in the url like this

?redirect_to=%2Fadd-new%2F

and I would love to be able to specify that parameter in the plugin as an redirect option.

So besides a site / backend option, I would love a site-parameter option, where the plugin will look for the value of a parameter in the url, and if it exists, it will use this as the redirect slug, and if not, it should redirect to a default site url specified in the settings.