Interesting idea, doubt it will get a lot of purchase as most of the prices I can find for Kangaroo Grass Seed are north of $500/kg, that's before malting which at least doubles the cost. Would make for beer in the civet cat coffee price range (totally OTT).
Not all grass seeds make good malt, ranges from some that are utterly useless, up to Barley that is really good at making malt (& beer).
Mark