Technically, there is at least one more engine we could utilize (2 with html variant) - gtkmozembed. That’s basically the underlying engine for MicroB but we would not need to go through the browser. I first want to iron the kinks out of the existing code-base before adding more engines (but if any gtk hackers are watching this, patches welcome !). The current engine interfaces are pretty basic, so I’m certain we can/could/should tweak flash performance/IO/etc.