I think it's a good way to go as backgrounds are mostly a cultural thing rather than biological. A sylvan elf gets his ranks in woodcraft or stealth because in comes from a hunter society IMO. On the other hand, I can see some cases where this is not so clear. Do the elves get their affinity with magic because of an magic-rich upbringing or because it is something imbedded in their DNA ?
More to the point, I think cultures mainly evolve in response of environmental factors. Philosophical or religious trends may also inflect the way a given culture evolves but basically, any rural living people in most kingdoms should have similar cultures and skills.
I would be interested in seeingbwhatnyou propose for your Marth background. I have not read much about it but the ice age it is undergoing is likely a leveling cultural factor.