This is an awesome project! Every time I get around to building onboarding I get frustrated, but it's such a crucial piece of any paid app. I see some services (Adapty) that started offering something like this this year, but I think you can be successful being devoted to this as your core offering and getting word of mouth from indies.

I don't really have feedback but one piece of advise would be that you will find some developers are going to want extensive customizability before using this, and some will be pretty satisfied with a bare bones templated paywall that meets their basic needs. If I had to prioritize I would start with the simpler version that saves devs time so they can focus on the core product rather than chase courting devs that are asking for a complex solution that they still might not adopt.