It's actually fairly easy to wire up a speaker cab. You can totally use the DRRi as a cab in the interim. It would be as simple as disconnecting the current speaker wires, then having two decent gauged wires attached to the speaker terminals and ending in a 1/4" plug, bypassing the jack completely. But you could also wire an input jack and install it on the cab, too. The speaker is otherwise relatively independent of all the other guts in the enclosure.
Hoped that helps.