I feel with the way maps are currently designed jump would cause more problems for SE then it would fix. They would have to redo the terrain in a lot of areas to prevent people from scaling walls they are not supposed too. Also theres a chance that they wont make it high enough to be functional because of the issues with size scaling. A Lalafell and a Roegadyn both jumping 6 feet into the air just seems wrong to me.
I have no problem with instanced jumping when your trying to jump down from a decent cliff as long as that cliff isnt too high.
Nier is the best game ever made.