Dragonlord: Input isn't so cut and dry on Linux. You have oldskool X11, XInput (the X11 extension, not XNA), and the Linux Joystick API. You can usually disregard the old X11 form and just use XInput, but XInput is hard to find documentation or code examples for (in no small part thanks to Microsoft's XNA input stuff). And the Linux joystick API consists entirely of directly opening /dev/jsX and parsing what comes out -- not exactly an elegant solution. You could use a middleware, but then you have to use that middleware's graphics implementation too, due to the nature of the X11 protocol. (With SDL this isn't really a big deal, but SDL's ABI isn't quite stable...)
Dragengine has some interesting design promises, but your featurelist is years away from what we need. In particular I don't see any mention of continuous open world support (think GTA series or Oblivion). That's going to be a killer app that's here to stay in the years to come.