If you build a custodial lightning wallet that makes taking sats over to on chain self custodial bitcoin wallets graceful.
Make sure that you do not have minimum withdrawl requirements.
Every solution that i have come across has this barrier to entry. Whether it be 250k sats, 50k sats, or even 25k sats. When you have limited income, or very few sats from zaps. Those minimum withdrawl requirements makes getting your sats off lightning and back onto on chain exceedingly difficult, or practically impossible.
I look forward to seeing what you develop. Let me know when it is ready for bug testing and i will help out. Take care and stay awesome.