Of course what you suggest is possible - the only possible issue is that your customers could share your template with others without paying you for it. Whether this is likely to be an issue I can't say of course.
It may be worth contacting Ninox about their Partner Sceme as you may be able to earn some additional money through an affilliate link.
I would be interested in a feature that allows developers to sell usage of their app as well. I've seen other low code systems that allow a developer to add separate "user accounts" into an online application. Some sort of version control would be helpful too, in order to facilitiate upgrades for all customers at the appropriate time. (Wish list item, of course).