Has anyone tried out the Plasma Obliterator Fortification at all? Seems like that might be a really good one to guard the backfield, maybe with Coteaz inside, and/or with a SpaceWolves IC with the Helm of Durfast (to reroll To Hits and Ignores Cover). It's AV14 and 4 HPs, and can take a Void Shield, but with that it runs at a Land Raider's cost.

Or would a Firestorm Redoubt be better for a Fortification investment? Of course those quadlascannons can't be fired by models, but that's some good antiFlyrant gear.

I read about the Vengeance Weapons Batteries, but they only auto fire at BS2, though 2 can be had in one Fort. slot, but nobody can embark on or in them. I think those can take debris piles though for some cover saves for models behind that.