I was playing with the SketchUp models on greenboy's website and came up with this.. The original box is unchanged as I just built on top of it, and I think with the inside of the bottom port slots and top "port" slots painted black, it wouldn't look odd from the audience.
1515+66, undo a few latches, flip the top, poof, 1001RB, or whatever you want. There's plenty of room for a 2U head and the ports are the same size on top and bottom of the cab. You'd also have room for cables or whatever.
Just an idea. More complex than just doing an airhead cab, but more stylish IMHO.
Awesome SketchUp is a fun program.
Another good amp for biamp possibilitys is the Invalid Link Removed
depending on load i think it can do 750watts per side or 1500watts Bridged. and they say its 2 ohm stable...so you could run alot of cabs with that. Has level controls and crossover freq too...not to bad for 549$
A good idea for the finish of your cab is to look at the original Invalid Link Removed
just plain old carpet..yuck...i like vinyl better