They do look very Rescuers: down under. Love it!
I do like the direct swap of tau for other auxiliaries, not sure how an Ork would reflect in the fluff seeing as there one of the races that Tau have deemed pointless in negotiating with (Argue it's a super intelligent Ork?)
Here's one of my basic conversions- Gue'vesa breacher! I took off some aquillas and added a big shoulder basically.