I like RSRD but agree, way too many lone merchants.In the begin of the war before US subs were seen as a real threat, lone merchants or unescorted pairs were common.As war went on this became less and less common, esp if a mid or large sized ship.
My solution to this in TMO was to open up the merchant layers with the mission editor and add escorts to some, esp the tankers.So got no more 10,000 ton tankers traveling from Java to Tokyo alone.Left some single but added escort to others, that way, less chance of running into singles.Fun to encounter small convoys of 1 merchant and 1 escort, this was pretty common.Sometimes if its abig important ship, 1 ship to escorts.Or two merchants one escort plus a plane assigned to the group.Really adds to the game.
In RSRD I tried this but turns out you can't change anything because it upsets everything else for some reason.I made some changes, it reset the convoys respawn from 0 to 24, never could get it back to 0.Not sure why but can't modify it, i was
about this to say the least.