Its been asked a few times, I made a thread years back on marshing yards, communications, different factories like Airframes, Engines etc.
Biggest problem I can foresee: adding these to existing maps, who is going to design them and where are we going to ptu them?
Secondly, our primary factories are clustered together, what I purposed was having Secondary targets (V-1 sites) spawned across the map along with the rail yards - however secondary targets get half the perks as bombing the Strats. Main reason is to cancel out those who want to perk farm.
U-boat bases would be a nice addition, they would take a TON of bombs to destroy the boat pens. Along the ideas of having random fleets run around the map as well - Transport groups of AK's and APs escorted by maybe a destroyer or two.