Single-submission will be indeed very useful, but in my case I needed a simple redirect (nothing fancy, all users get redirected somewhere), no security involved, simply from the usability standpoint.
A returnURL variable somewhere would have been nice. (It is one, but I think it is used for the External Authentication)
As a quick workaround for my case I was thinking to put some redirect function in a successful submission that redirects to a URL that is set in the config.json file (if set, otherwise dont redirect) somewhere around:
What do you think?