It seems to me as "just" an infrastructural challenge, the search keys or categories that I would find useful on a repository/scenariodepot are "Balanced for H2H", within that one, "(Semi-)Historical", "Casual" and "Competition". "Single player" that would have "(Semi-)Historical" and "Casual". A divide between scenarios and mods would be welcome as well for browsing. Not to mention modpacks; who wouldn't use all Aris'mods anyway?
All entries would have tags with these categories and all the settings used; Map size, duration, time of day and so on. In this way it would be possible to choose a scenario based on ones preferences without getting spoilers. A review/shared experiences section in which spoilers are allowed would be present as well, it would be up to the decency of the H2H-players not to read the spoiler-reviews before having finished the scenario.
This last bit may be tricky for some but I actually don't even watch ChrisND too much before a release because he uses maps that will turn up in the game.
Repository feedback and the right info without spoilers do work well with for instance AD's sweet little infantry scenarios for Gustav Line in the repository. Might be because of the small size and limited complexity.
It occurs to me that Battlefront might like this as it would also provide them with feedback on the stock scenarios. "The passage" from CMRT is utterly unbalanced for H2H and now everyone has to find out for themselves which might reflect bad on the game.