>>714846If you're REALLY desperate, there was a little bit more than just the 3 episode OVA.
There's the comic I posted above that was a promotion to the show, the soundtrack CD that has a mini audio drama on it, 3 audio drama CDs, and a novel.
Skimming through the novel, and hear some of the audio drama cds, I think it's entirely possible that more can be done. The trick is, as you said, can more be done while still keeping it good. I wish Yuji Moriyama would get a sudden spurt of genius and make an awesome sequel, but that's probably a wish that will go unfulfilled.