So I picked up 2 chimeras in a trade a while back, and I've decided to Forgeworld them up into a pair of the new artillery tanks. For my initial list with the new codex, I'm going to try to squeeze in a company command with an officer of the fleet, ratlings, stormtroopers or grenadier veterans in a valkyrie, vendetta, or chimera, an infantry platoon with a couple lascannon squads, a demolition vet unit, a recon sentinel squad, a couple hellhounds, and as many demolishers I can get. With that in mind, here's a few options for 2 more tanks (pics from the FW online store):
The Medusa would make a great anti-vehicle tank, firing indirectly with the bunker buster shells, but with the lascannons, melta guns, and demolishers, I'm probably good on stopping armor already. Still, the model is pretty cool and relatively cheap and only a bit more than the basilisk points-wise. I could even get a third conversion kit and change up my existing basilisk to make a trio of these guys.
The Manticore is a really neat model and several large strength 10 blasts a turn sounds like a good time, but they're fairly pricey on points and dollar bills. I'm not ruling it out but probably a long shot.
I think I've saved the best for last. Together with the hellhounds and ordnance they could peel the numbers off horde armies and put the hurt on skimmers and nob bikers, too. I'm really leaning towards a couple hydras as a third heavy support slot. At 75 points base they're a steal. Unfortunately, like the manticore, 2 kits would run me about $85, which stings a bit.