PS2 limitations.
Sorry, had to say it.
It would be a bit tough to implement, and would require larger volumes of data on their servers due to more model rendering for each expanded mog house, etc. (not a real big deal, but something to think about). Could it be done? I'm sure it could. Will it be done? It's SE... so no :P
A neat idea, just something I don't forsee ever being implemented.