I like this feature. The bases that are within 1,000 to 1,500 miles of the front would be easy to spot construction, via subs, coast watchers and search aircraft. This encompases most of the bases that matter. The bases that don't matter are: SE Pacific bases. If you're developing them in secret, to run ASW and Search missions, then I can see your arguement. But, building up a REMOTE base to run search ops seems kind of rediculous. It's remote, meaning no enemy units nearby to spot.
Now, if you're arguing to build up Stewart Island as allies, when Japan holds Lunga, then I don't see your arguement. any half assed plane from Lunga will see your work in progress at Stewart Is, Duff Is, etc.
Building up the French polynesia bases should be relatively secret, but which IJN player will be stuffing that area with subs?
The bases in Manchuria, in theory, could be spotted by Russian planes. There's really not a lot of places on the map that can't be reached by subs, coast watchers or planes.
Anyway, that's my opinion, for what its worth.....
The older I get, the better I was.