My two pennorth worth is stick to 1/50. It works well enough with 28mm figures and it has definite advantages from a commercial point of view. You already have an established range of vehicles in 1/50. Wargamers, being the gadflies that they are, will likely mix things from your Vietnam and modern ranges for other conflicts. You already do M-113s, M-106s etc.
Customers are also likely to mix with other ranges. Solido, TAG and the new Gringo 40 ranges are all in the 1/48-1/50 bracket. Going somewhere else seems a bit perverse. Gaining leverage from other ranges seems sensible.
Personally, I’m not wedded to any given scale, I freely mix ‘n’ match but that has more to do with availability than anything else. That said, given the choice I’d like to see a standardised scale and 1/50 seems to be the choice of most existing manufacturers.
Dunno whether the Corgi sits high on its suspension (a problem with at least one well known 1/35 kit) but it is worth pointing out that the M-48 is a honking big vehicle.