ORIGINAL: morvael
A free-for-all production system isn't necessary. What I would like to see is a semi-historical requisition system, where the allowances are decided by history and the player can request (not build) only historical units (giving up units used to build up if necessary), up to the limit of given period, give or take a few % by paying extra prestige (VP) for getting some units a month earlier. So, if the Soviets had 20 Tanks Corps in December 43 (just random example) and I have only 15, I can request 5 more to be put on the map immediately at no VP cost, ask for a 6th by spending extra VP or order only 3 and getting extra VP for every turn under the historical limit. Basically a reinforcement table that a player can strech a little and define order in which units will come, but not their maximum number.
I nice thought, and interesting for the base campaigns, but I disagree here. I'd rather think along the WiTP-AE lines and get full control over production, research (or not building newer models), and especially over ToE "upgrades". This would be the "cherry on the cake" solution to me, of highest value. Also for games against AI, these controls would make the later grand campaign years much more enjoyable -- a clear plus point for buying WitE2 that would be.