Check out the Sicaran Omega Tank Destoyer. Lethal at close range but not much of a threat over 24 inches. Yes its a fast vehicle, but when you move it up to strike, especially if you are in a drop pod meta, it can really open you up to a DDM type of an attack. Definitely love the aesthetic and with a name like Omega, I will definitely be getting one for my Ultramarines.
There are experimental rules for both Horus Heresy and 40K.