Aloha,
Rocoteh
I plan to add some AI-versions later this year.
This should offer challenge for veteran-players of the scenario.
Maybe mobilzation should be taken out to make the regular scenario harder to play.
I welcome comments on this issue.
I think you are on the right track in reducing the shield output of the individual cities.
The biggest problem of this great scenario is its huge scope, being in command of 2000 + units and lots of cities just takes lots of time and makes me settle for the good solution as opposed to the most efficient solution. Fewer units is a good way forward towards more micro management in relative terms.
Reducing the output will put more emphasize on cost/value relation as opposed to only producing the nominally strongest unit. That way I do actually have a reason to build my beloved He 218

Ironically this scope is also the greatest strength of WW2 global
Taking away mobilization vs. reducing factory bonuses:
pro:
* Factories etc. still have to be build in order to boost production as opposed to the effortless mobilization.
* Importance of heavy industries to the WW2 war effort (coal and steel -> hills, mountains) is better reflected
* A decision to bomb the **** out of a city will cost more in terms of time to bring it up to speed again
(to have a meaningful output for the cheaper units)
* One (ore ones ally) can positively react to peace offers by enemies without the production penalty
* OK this depends on the player: Fewer resources makes one pay more attention to one's core crack troops (combined arms approach) in terms of protecting it and auxiliary troops will have to be used to a greater extend.
* It spares first time players the frustration if they find out about the special qualities of mobilisation in this scenario well into the second or third game (That happened to me, thats what you get for not reading the manual

)
con:
* reduces the amount of units
Bottom line:
Go for it!
All the best
Baldurslayer