I would suggest in the appstudio menu option, add one option “add 4 debug built only for today immediately”. It would then go through the payment process. And, when exceeded this 4 debug add on, display a warning message.
Which would gray out in demo version.
What about voltbuilder, indy to Pro menu option. And voltbuilder, pro to indy menu option, which go through the payment process.
More good suggestions - let me see if they can be done.