On adding a hit differential calculator, I think having this additional info in the game would be quite interesting and useful even though I do agree that not all dice luck in the game is equal. Its more information but will sometimes lend itself to a misinterpretation of the actual luck of each player.
I do think though that if there is a way to avoid counting superfluous hits, that would make it more accurate. Some dice luck doesn’t matter to the game and so shouldn’t be counted. If 6 fighters attack one destroyer the consequences in game terms of a lucky roll of 6 hits is the same as an ‘unlucky’ role of 1 hit or an average roll of 3 hits. It doesn’t actually matter to the outcome of the game but the measure would make it appear significant.
A TUV differential might have other problems, but it would solve this since superfluous hits aren’t going to impact on it.
But I thought another way to do is to take this hit differential counter and modify it when the hits exceed casualties in a combat. That is to say, in combat rounds where the expected number of hits and the actual number of hits both exceed the number of casualties taken, the hit differential of the victor in that combat round doesn’t get counted in the hit differential. This assumes we can break it down by combat round and I’m not sure if that can be done.
If that can’t be done then perhaps in situations where the combat only goes one round, and the expected number of hits exceeds the number of casualties, we could just ignore the hit differential of the winner of that combat. That would at least remove all situations where you send a stack after a lone unit. I think?