I'd drop a tankbusta in each squad and one of the big mek's big choppas in order to add two bomb squigs in each tankbustas unit. Those squigs are so damn good and also cheaper than the bustas that they can't stay out of the list

They hit on 2s with the re-roll against vehicles and
D6 damage, you can also kill them instead of a busta if you have to take 1-2 casualties after the wrecking of their transport. I never leave my bustas without them
Overall I really like your list, I usually go with some vehicles and lots of artillery as well.