For heavies, that is true for most of the Hordes factions- a second 3 in 1 plastic kit will be difficult at best, unlike the WM factions. Seraph/Angelius/? doesn't really work, and Rhinodon/Archidon certainly doesn't. Not like a centurion/avenger/hammersmith, anyway. Even the Satyrs for circle are very different models.
I think so. At least the Driller and Rockram are.Given that the Rockram, Driller, and Avalancher are all effectively the same chassis (or maybe they actually are - I'm not sure of their stats)