overall i have seen hundreds of replies from people complaining to devs about why they cant keep historical accuracy with new progression system, or why cant they keep old progression system or whatever else problem they had under historical accuracy umbrella.
so i will try to explain why historically accurate battles are unsustainable.
current campaign progression is unsustainable cause it splits playerbase in 6 different campaigns with 6 different queues. it was good at beginning cause with low number of campaigns playerbase could sustain it. but with every added campaign it splits playerbase even further and you are less likely to see humans in your or opposing team. also there is problem of repeated grind for same items and equipment imbalance (stuart vs tiger). but it mostly keeps historical accuracy (except for few weapons/vehicles)
solution is either to stop adding campaigns or even remove them. totally unacceptable to devs and probably to quite few players.
weapon tree grind system. easy fix for multiple grind across campaigns. so why is it a problem to have historical accuracy for it? cause players can make any composition to squads they want. most of the battles are relatively unique cause of weapons/vehicles they fielded. so even if player makes e.g. 1941 squad for moscow, it could be historically inaccurate cause e.g. t50 was made in time of battle, but was in use in leningrad, or fedorov that was prewar weapon was reissued from reserves for service in soviet finnish war in 1940, but was mostly destroyed in that war.
so if you cant use year, you can mark specific weapons with campaigns they were used in? yes, but there is problem that by doing so you will be basically replicating old system with 6 queues now (8 till end of the year and more next year). it may be more flexible, but overall it is still 6+ queues and still doesnt fix issue of game balance (pz2 vs t34, tiger vs stuart).
so do you keep historically accurate MM or do you switch to something else?
conditional rating MM (or commonly known as BR in WT)
overall fixes balance issue (still need to see exact implementation cause it could be open to abuse) at cost of historical accuracy. not all weapons with higher BR are made later in war (see m3 smg vs thompson), so it cant be historically accurate if you want to use it to somehow artificially limit campaigns by BR. but overall it is mostly accurate cause low BR weapons usually represent early war weapons, mid BR may represent mid war weapons and high BR can represent late war weapons.
considering that one helper unofficially said (so speculation for now) that campaigns shouldnt be totally random, so if you equip late war weapon, you are more likely to end in berlin. i will use graph of @coldestwinter from another topic to make representation of how it will probably work according to that information
someone with BR of 10 will be matched only on berlin, with BR of 8 could be matched in normandy and berlin, with rating of 4 could be matched in moscow, stalingrad, tunisia, normandy or berlin with similarly equipped opponents. so if you have BR of 4 you will probably end up withing ±2 BR of your opponents.
so if you are still asking for historically accurate battles, try to give algorithm on which MM can function even with addition of new campaigns and try to give estimate of how many players need to queue at any given time and if it will fix equipment imbalance.