ADnD 1e had large sized damage with a weapon dealing more damage to large or greater sized creatures and I see a 'playtest' booklet with concepts like adding dice chain +/- d (dice type) instead of rolling twice, so why not include large sized weapon damage. 2-Handed Sword does 1d10 (S/M) / 3d6 (L+) with huge, giant and other larger sizes all rolled into L. This seems like the perfect adventure series for this, plus you get bonuses to AC being a small guy or gal (dwarf, gnome, and other small stature races perhaps goblins, halflings, kobolds, etc.) and I'd say 'any small sized humanoid' gets +4 AC vs Large sized or greater creatures, or you could say +2 vs Large and +3 vs huge and +4 giant sized or greater to be more nuanced. Add in a Dwarven Thrower and Giant Slaying weapons and you are ready to rock and roll out of the way of the breath weapons and area spell effects.