Personally, I'm fine with not really caring about the mementos. To me they're almost more like a handicap, or like an alt game mode. My current game I slotted in one that gave Commanders an extra movement point, because that felt like it should be a base game feature I feel they're better with a little more movement. I haven't tried out any of the others, and don't even know what those unlocks actually are, and don't overly care.