They could be another Dedicated Transport, that you can purchase by itself as an "FOC" slot to be determined. I'm still digging the idea of Elite instead of Fast Attack. It's not a Valkyrie.
I was pretty sure the Hades used to have a Large Blast upon arrival, and that models that survived had to be moved by a minimum distance to get out of the way of the drill. Something like that would work if you had a Melta-Cutter on the front, but I don't know about a drill. Just seems like you'd get thrown out of the way. A big-ole Melta-Grinder-Combo coming up from below would, at the very least, lead me to believe that the very mouth of Hell was opening beneath me.
I think a single, Large Blast Melta Hit upon arrival would be reasonable, with a 12" small blast firing out of the front in subsequent turns? It wouldn't make sense, to me, to have additional weapons on the sides because they'd be torn off while tunneling. If you go with the Fortification idea, something I also like btw, then it could have weapons pop out, but you'd pretty much wind up with the drill facing the sky, which wouldn't allow it to keep firing as a weapon. Not a bad thing, but it would probably be a one for the other situation.
If you like the Termite / Mole idea, they look functionally identical to subterranean Drop Pods. They burrow up, blow the hatch, and everybody gets out of the pool. Again, like Drop Pods, the relatively slow emergence would probably prevent their use as an Assault Vehicle. Ceramite plating is mostly used on craft that endure orbital entry, and I don't think that would be the ideal scenario for anyone aboard.
"Out you go boys, point the drill at the ground!" "Umm, Sir, We don't possess flight control, and I'm pretttty sure this isn't an orbital landing craft..."
But man would you ever deserve to be a D-Class hit on whatever you landed on.
If you give it weapons, it's pretty much a deep striking Chimera. If you don't, it's basically a Drop Pod that can maybe / maybe not move upon arrival. I honestly think it would be fun to turn it into a battering ram for vehicles / MC, allowing it to make a special tank shock rule kind of like the old Ork Deff Rollas, except with a big scary melta-shooting siege drill on the front... but that's just me. Death or Glory attempts at -2 ld, something like that.