The problem with adding the padjal into the game as a playable race is they would have to be restricted to being Gridanian, as it's the elementals that turn people into them as their 'chosen' - because of this, the padjal function as Gridania's leaders, making them less inclined to travel the world killing monsters and stuff that an adventurer does.

No doubt Yoshi-P probably realized that right away as well, and hence his reluctance to do so (besides the fact that they're indeed still very human looking).