If you are looking to be able to emphasize/de-emphasize individual projects, I do not think that would be realistic, because it would be relying on hindsight. We all know now (or at least think we know) that the Germans should have gone over into a "total war" economic mindset earlier, and focussed on building Panther Gs (but with simplified engineering), FW 190s and ME 262s. Oh -- a durable 4E bomber woulda been nice too. But to be able to project that knowledge back in time does not make a lot of sense to me. I don't mind grand-strategic "what-if" games, but WitE does not seem to lend itself to that.
I don't disagree that it would be ahistorical for both either side to have full production controls.
I personally think it'd enhance my enjoyment of the game a great deal though.
Frankly I'd happily pay for the game all over again if the new package included reasonable production controls (for both sides).
I'd be quite happy with WITP's "stay within the lines" production controls e.g. no need to include ahistorical production projects like the ME-264, I'd like to be able to pick which AFV and planes my factories produce though.
I think this is just a matter of personal preference. To me it is much more important to accurately model the actual historical events, than to add in "what ifs." Also, once the what-ifs get added in, play balancing becomes exponentially more difficult -- you can see from a lot of the comment threads that people are basing their opinions on a handful of games played for 20-30 turns at the most (with a few significantly longer exceptions). It is hard enough to deduce from these experiences where the modelling is off and where it is just a matter of bad luck or bad play. If you start adding in production variabilities, it will be even harder to compare apples to apples.
But that's just me.....