Interesting thought about creating a ladder for historical gamers. I think a lot of the posts here have questions of how would you do it? Your idea of a historical battle may different than my idea and the next person's idea. It would be difficult to gain a consensus.
I think a ladder by it's very nature is a way to rank who are the better players at combat mission. I define this as those players that know what is the better equipment to buy for a situation and how to use that equipment. Does a high ladder ranking make you smarter historically about world war 2? Of course not. Combat mission is just a game with different units. It's the same as Diablo 2 or Quake (gasp). As much as I would love to play a historical simulation of Custard's last stand I don't want to be the U.S. Cavalry for too many ladder games.
My suggestion is that historical players and those who detest gamey tactics don't bother with a ladder to begin with. Have a forum where you can have campaign ribbons, medals or decorations for battles you have fought in. That way you would see who is the best role player if you wish to judge yourself against other historical gamers. If your fighting in the meta campaign you could get a ribbon for that. For those who are good with scenario design their should be a medal for that. Or maybe you could get a purple heart after you achieve a certain number of total losses against tournamenthouse ladder players. That way you can sit around on your historical butts drinking your british tea and detesting those gamey powergamers over at tournamenthouse.
In conclusion, non gamey combat mission is a lot of fun but I would think it would be difficult to find out who is the least gamey player out there and put him on top of a ladder. Historical, non gamey tactics and ladders don't mix because you can't define every gamey tactic and have more than three people agree on it. (generalization of course)