I think this is very simple, if you want to use services that are marked as pro then you need to have pro version.
By using pro you are making all us others dump for paying for it and you are slowing down development.
A pro feature it supposed to not work in free version from the beginning. If it's works, the users can think the pro tag it's a mistake, or it's something else.
If it works for months, you can't simply pull the trigger and put offline thousands of websites. You can of course, but the consecuences are here.
Maybe a better aproach it's to communicate the thing, and give a few weeks to the users to change their servers. I think that many people would have bought the PRO version without problem.
Now? Stay away, very far way, from this panel.