This sounds like a good idea. I do wonder if enough people would sign up for it to be a worthy venture because I think the main issue with ads is I think once you add any price at all dramatically reduces participation even if it’s not about cost some people just see the payment and immediately disengage.!
1. build a userbase, free product
2. once userbase get big enough, any new account requires a monthly fee, maybe $1
3. keep raising the fee higher and higher, until you get to the point that the userbase is manageable.
no ads, simple.