Right, ok then. My advice, if you can get Landspeeders and Bikes, use them. Landspeeders can deepstrike in and unleash heavy bolter/heavy bolter death from Turn 2, but they can also be popped open like ripe watermelons.
Bikes, on the other hand. Well. Turbo boost and their armour save becomes Invunerable, they move 24". Problem is they can't fight.
Turbo boost him to the back of the board, close in, and assault. I think that Tau are going to have a few problems with WS4, T5 enemies in assault. What's more, I believe the Sergeant can now get Artificer armour... and a powerfist...
So basically, bikes are your friend. If tyhings go wrong and the assault lasts a while and he moves his troops away, deeppstrike Landspeeder. Abuse the Chapter Traits rules, I'm sure you can make it sound like fluff somehow :p
Wargaming should never be combined with your love life or a pot of honey.