Especially one that old, the connection will be pretty simple. Most likely just a straight flat ribbon cable from each to the MBB. You can definitely extend them, though it will probably involve some delicate soldering because of the cables they use. I have seen it done though, and you'll have a fair bit of cable length to learn on (at least a few inches). I would cut it in the middle and extend it with some old IDE cable scrap. That way you don't have to worry about the connectors on either end.
For the keyboard, I had a thought. What about putting it on a motorized or spring-loaded panel that slides out the front? That would keep it out of the way when you're not using it and not disrupt the design on the top when you are. ...plus, it would just look awesome.