We are planning to integrate Keychain, but we have to get through our priorities first. As far as integrating Steem Engine tokens, I personally like the idea, but again those pesky priorities ;) It would seem to me that just integrating Keychain would be the ideal solution as that extension has support for Steem Engine tokens. In many ways, we're always going to be the last to adopt certain things because as the focal point of the ecosystem we have to be the most careful with user experience and user security. Thanks for the ideas!