I think this might work better for responses too :P
1. Oh there is very much so a difference, I agree with you there. I just wish the girls were more inline with muscle development as the guys are.
2. I've seen plenty of people in muddy environments, having lived in Florida near a marsh myself, and it's not easy for anyone. At least though, assuming the person is of proper muscular strength they can pull themselves out of the mud much easier. Plus, smaller folks just generally don't do so well in combat, there's a reason why Lalafell rule via intelligence and magic and not through physical strength :P Though thinking about it, didn't the duskwight Elezen live underground in caves? It must have been pretty awful for them at times!
3. In the 1800s, ie, the various plains natives were still pretty active in nomad traditions, the few bits sources I've read specifically in reference towards their nomadic lifestyles as well. The area the various plains tribe weren't the best in resources either, though the few bits of information I've gotten seems to indicate that the mongols were on the shorter side of things, perhaps seasonal climate played a big role in that? Looking at it, it might be a bit weird, as both the area that the various plains natives lived and the Mongolians were classified as Cold Steppes as opposed to Subtropic Steppes..
4. Oh no, I get you, it's a ton of fun! My biggest issue is I'm not a fan of SE making them like that for that reason >.>
5. That would be the case if all Domans were farmers, which I doubt :P. Chances are the Raen that worked in the fields were more muscular, while those who lived in cities were more lithe. Honestly the subject of machinery in FFXIV is also weird.. We've got airships, I'm sure there's some form of machine to help farming too, like little Mammets that pick the grains for you or something! I can see the appeal to that, maybe in the 3.x series character customization will receive a nice big overhaul and we can have our Au Ra better match our wants! (Pls SE ; ; )