I had been thinking it would be good to have a Gigantic trait that boosts hit points by some 50% and damage by some 10% but with around -15 from melee and ranged defence. I think such a character would have an equal chance to have either high or low max fatigue (along with additional traits that can either enhance or diminish fatigue factors). Such a trait would make it more viable to build characters primarily around toughness.
As for evasive runts, I’ve noticed that a lot of thieves seem to be Asthmatic these days (and sometimes Short as well).