Yea im thinking of a new plan for these…
Just like techs you spend 5 IPC and roll each turn as per rules…Also, perhaps some limitations would exist like neutral major nations ( USA, USSR) cant participate until activated.
if you roll 6 then you roll a D8 and you get randomly one of these new units. The new sculpts could even be on cards.
Each unit would cost the same as normal units… heavy tanks still cost 6 IPC… the deal is if your successful, you can buy the first one for -5 IPC, and can always buy more for the original price.
So if you draw Battlecruisers, you pay 11 IPC ( 16-5) for the first one, and can build them from any turn forward.
It is not Historical because some of these would be available in the early war period.