
Simple fact is, all mechs should be given the maximum protective hitboxes they are capable of, as intentionally gimping hitboxes is a stupid idea for balancing. Then when one has decent hitbox designs, one can realistically see what mechs need defensive quirks to account for poor geometry, the same way mechs with low hardpoint counts/poor locations should more likely receive quirks than those who have good hardpoints.
Further more, it's lore role should be considered when deciding whether a mech should be offensively or defensively biased when it comes to quirks. The Rifleman is a good example of one they got mostly right, with it being the original literal glass cannon of Battletech. No structure, but solid offensive quirks. The Archer is a good example of one they got very very wrong. (As honestly are the Marauders and Warhammers)