The point has been made elsewhere, but is worth repeating: what you appear to be sketching is the end of your software. Your model doesn’t scale. I have perhaps fifteen apps I use regularly. Like most people, I have a finite budget. As ownership cost increases, I will terminate ownership on a lowest-utility-first basis. I can’t (easily) substitute specialist software. I can replicate your software’s core functionality with a freeware editor.
More fundamentally, I don’t want your software to bloat out. Its simplicity is why I bought it in the first place, and it does everything I need.
Bring your passion and talent for clean interfaces and flexible information structures to other challenges. Mac is crying out for a decent contact manager, and a simple database, and whatever it is that TinderBox and Devonthink do that people rave about and I can’t fathom, and an Evernote that isn’t deranged.
More geese to lay eggs. Not more eggs from your shortly-to-expire goose.