I feel like every Khador caster has at least one spell or ability that maximizes warjacks - most, it would seem, would prefer running only 1-2 (correct me if I'm wrong).
So far the ones I'm not sold on putting the Conquest with are the Old Witch, Karchev, and maybe Vlad1 (maybe). The Old Witch has Augury which is really cool, and it could be fun to place Creeping Barrage templates down on models stuck in Field of Talons. And Field of Talons and Gallows can help the Conquest engage enemies. I guess its not that I think it would be bad, I think I just need to see it in practice since it feels like you have to earn it with her.
Karchev has Unearthly Rage and I guess Conquest screens the big guy, but what else? Tow doesn't work here, and Sidearms doesn't offer too much. The feat gives a free charge. I think you're better going with multiple heavies than a Colossal here. I feel similarly about Vlad1; I think you want multiple jacks to maximize his feat.
I'm just spitballing here. I haven't played my Khador in a while, but this guy has me excited to play them again.