True. There are a few campaign mods in the works. Hopefully a couple or 3 will combine since it's a lot of work.
I have a start at one right now. I am altering the stock layers. Large changes in ship content, and most units will be found zig-zagging. I use multiple routes, I even have some TFs or convoys put in to a place like truk, spend a few days, then leave for another port.
The 3-4 escorts for a single ship thing is possible, and I do it. In the random layers you can make say 4xMutsuki DD as escorts for some merchants. 1 merchant occurs 100% of the time, another 15%, 3 different other ships at 5%. I might set the DDs to 20%. Maybe a subchaser or minesweeper (I have the 2 types changed to be "corvettes" so they both will act like escorts) at 10%. When that group generates, you get 1 merchant, but you might get no other ships, or you might get 4xDD and no other ships, or you might get 1 DD, 1 minesweeper, 3 merchants.
So it's possible to get highly variable convoys. I also add some combatant ships to convoys that go to palau, truck, kwajalein, etc. A small chance for a minelayer, or CVS, CL, or possibly a plane ferry (Akitsu Maru).
You are right about the losses in 1943, for all the reasons you mention. There were also simply more patrols, and possibly a higher % of "aggressive" patrols. The patrol areas were better picked for making attacks, and possibly more counter attacks happened as a result.
I'm also looking for an idea set of mods to AI capability. I want to have them spo and attack frequently, but succeed only rarely. Easier said than done
tater