Suggestion: Add credit-card processing. As a developer, I would benefit from being able to implement a single payment integration that let my customers pay how they want to. Credit cards are the obvious biggie, but it would also be huge to be able to e.g. receive European bank transfers as a US-based business. My dream "OmniPay" would also handle PayPal, Venmo, etc. as well, all with one integration.

Much as I'd like to try accepting cryptocurrencies, I'm definitely not going to manage multiple payment processors to add support for what (I would suppose) would be a tiny fraction of my business.