As far as I can understand from the technical details, GatePay will support bitcoin but how will you make everything in your whitepaper work? Can you please elaborate it? IMO, Since the buyer needs to connect to the vendor's node first, this project will require you to ask for the help of experts with lots of achievements in coding blockchain related projects. Also, will GatePay support other cryptocurrencies besides bitcoin?
Our protocol is called "protected transaction" and it has two implementations which are decentralized and centralized implementations. For decentralized one we need to build an open p2p network which will be handled in the future. Right now GatePay uses centralized implementation which we store "protected transaction" (2nd transaction) on our server (not private key, signed hex transactions which are ready to release). Our servers run nodes to detect double-spend attacks and release these transactions in double-spend case for merchants. Its an already working product supporting bitcoin, ether, litecoin, doge and dash. You can get it from app store and playstore as a software wallet.
https://itunes.apple.com/au/app/gatepay/id1306809030?l=tr&ls=1&mt=8https://play.google.com/store/apps/details?id=air.gatepay