The main problem with the Planar Binding fix of assuming certain things about outsider behavior is that its basically a stealth nerf. A player might come in with the expectation that the spell works one way and then get slapped by the equivalent of 'rocks fall, everyone dies' as a million outsiders converge on them and crush them for their hubris, but that doesn't really make for good gaming.

For me though I'd just remove the ability to compel behavior from all of the outsider summoning spells, make it clear to players that you have to pre-negotiate the spell with the summoned being, and that you can get the same one each time so that pre-negotiation is actually useful.