I think the best option would be to remove bonus HP from STR and IF (maybe reduce IF to +1 HP) and instead make IF the requirement skill for armors. The best armors would require 7 or 8 IF like the "best" horses now do (or did at some point). That also means really heavy armors would need to be objectively better than medium/high ones, unlike now.
Of course that's technically not possible, though.