So you need to disembark at the start of your movement phase. I wonder if assault vehicles get some bonus or if that is even a thing anymore.
Also, the genestealer rules make for something great. Finally genestealers return as an elite killing machine. 8" movement, 3+ to hit, 3 attacks base. If you have more than 10 in the unit, they get FLurry of claws and all of them get a 4th attack. And if you add a broodlord, they all get +1 to hit! Add the 5+ invulnerable save and its incredible!