It's weird, but consider this, about Epic, we had this evolution:
Adeptus Titanicus - Space Marine - Space Marine 2nd. - Titan Legions - Epic 40k - Epic: Armageddon
It started out as plastic box sets and the majority of your army could be built with those £5 army boxes back in the 2nd ed. days. It was the later editions from 40k onward which moved all the vehicles to metal.
If they could just make a few sprues, you could have most of the infantry and small vehicles variants packaged up neatly in cardboard boxes like that all over again.