I'm not sure what you mean by "more powerful".
I had another look around, and it turns out we can integrate CEGUI, with a little trickery as to what OS the user is running..
Apart from that, I can really only see the need to add sound, physics, and scripting... Sounds relatively easy, as is scripting with either AngelScript, or Lua & LuaBind.. Physics may cause some trouble, however..
On that note, no one said we had to stick with ODE, there's lots of other alternatives out there - Newton, OPAL (ODE off shoot), Tokamek, etc...
Hell, if we couldn't decide on what engine, we could stick with what we have (I hate to waste Amarth's framework), and simply change the physics Library..