The Starfall has the DPS of a Prowler main gun. Are you absolutely sure you would like what is essentially a short-ranged double Prowler gun on the Sunderer? Don't you want something less powerful, like a double Halberd? Also what exactly do you expect the NC and TR to do with the Buzzard and Pillager? Pillager is so short-ranged it can only be used against enemies almost against it, which means the gun depression is going to be a serious issue. The Buzzard is tough to control, slow, has little chance of successfully killing infantry even with direct hits and isn't really of any use. At best you can stand near a doorway and lob shells inside at infinitum, but the sad truth is that a double Lasher would likely be better at that role than a double Sunderer-mounted Buzzard.
Was about to say pretty much what demi did, A blockade sundy with double Starfall would eat MBTs for breakfast. While Pillager is just kinda "meh" and Buzzard is just an inferior Bulldog. Currently it wouldn't be very balanced to add them to sundy because TR and NC wouldn't even use them, But VS would once again have the Battlebuses of years ago, as a faction exclusive. If pillager and Buzzard got buffs though, sure!
I think weapons based off empire specific LMG would be a better choice for sunder. So TR would have chain guns, Lasher for VS, not sure if the NC Jackhamer would be a good weapon choice for a sunder perhaps a NC could use the phoenix on it.