I agree that the AI vs AI battles are absolutely awesome. I had witness many battle like this and there was no mod to control it, it just happens. The most impressive was in MNostrum where the Luftwaffe regularly raid Malta, here is a picture from a longer set I posted a while ago...the whole port was in flames like a mini Pearl Harbour.
So this is where I try to adjust things for now. The traffic is huge in SH5, but mostly on the allied side. Now I try to increase the kriegsmarine traffic including taskforces, so we can feel that we are part of a war and not some lonely pirates. Problem is ... there is not much room for german traffic, at early war there are only few german active ports and not much destination to send german convoys.
I also set up few fast generic destroyer raiders whom will hit the brit coast, but Im not sure how realistic is this and also.. they may steal our targets. They can decimate a whole convoy in just few minutes, then leave. And having a balance it requires a lot of testing.
Anyway, redoing the campaign and implementing all these great ideas written down here it require a team without any doubt, like GWX was. And even so, would take months.