Ok cheers Silent I'll give that a go, I guess if it's all there from the start and stays there (I still get the original start-of-war loadout options for the 7c on my 'progressed' campaign) then it's a partial win. SHame to lose the historical dates activation though. The thing to test is whether it continues to work when you end one campaign and progress to another.
You're probably right though, it's a promising line of thought. If the date difference in OHII somehow knocks the equipment calendar out of whack when moving to a new campaign, it would mean that to have proper access to upgrades, you'd have to start a fresh campaign each time, losing all your renown/crew upgrades/tonnage score etc (it might be worth checking to see if this happens with just the stock upgrades too).
This is basically what I've done with Op Drumbeat, and so far all upgrades are appearing normally. But I'm a bit miffed to lose my score and medals etc (I still have the save, of course). Hopefully the above will work, but if the problem isn't the dates listed for each equipment piece, but rather something in the transition between campaigns that's causing it, it might not make any difference.
Any thoughts on this Trevally? You know the campaign better than anyone here!