I would very much like a payment gateway which enables me to transparently use XMR, to send to a BTC address, and to receive BTC in the form of XMR. It's a relatively simply thing to implement, and makes it more practical to save primarily in XMR.
Implement it. I would run it for the community as stable clearnet service and HS, to support the community/ecology.
(In normal TX limits. I dont have super much BTC or XMR.)
This is pretty much just an exchange API, yes? Are you comfortable with the poloniex pricing used for it?