Grading campaigns by their difficulty is a little bit dodgy IMO - while I don't have anything against having your own personal lists, I'd like to point out that the difficulty of one campaign might vary a lot between FSO builds, player's FPS and even just the viewpoint (I am under the impression that players were far more tolerant of tediousness ingame back in the olden days).
Even with as much attention to not impact balance in any way, SCP is inevitably going to bounce the mods' balance a little bit, which we've seen happen, by rooting out strange edge case behaviours or outright bugs that might've made past campaigns more or less difficult, with some cases even relying on these bugs for their missions to progress (Aftermath Reboot and Homesick are the ones I remember dancing around a little).
Instead, I'd like to give a happy smile medal to every campaign that would normally have a rather steep difficulty unless you pick long range missiles, when it becomes more of a point and click adventure game.