Isn't this possible now? When I click a link in the Gmail app, it offers to open it in Chrome.
So as it currently works on iOS you cannot say to OS: hey, I want to use this app for http, instead you check if there is an app that handles "googlechrome(s)" scheme, and if yes you can replace your http(s) in URI to googlechrome(s) and then it will open in Chrome instead of Mobile Safari.