This isnt so much about what they "want" but what they "can" do.
I'm not great with all the technic-details, so if anyone can explain them better than me - please do so!
The general problem of this game is that its build on a not-so-great code from 1.0, so quite a few things are rather limited because the code wouldnt need to be different for them.

When it comes to your character model there is only so many variables that are possible to keep the data at a limit that the server can still handle - so for example: elezen can adjust their ear-size, but Mi'qos and Au Ra cant (but can instead adjust their tail). Its almost a trade off for each race how those limited number of variables is "filled", so to speak.
Pretty sure they would love to give us more options, but they cant because the code (that cant easly be changed) doesnt allow for it because for whatever reason the 1.0-team didnt build it that way.

Now, however if a f2p starts with a "fresh" code and wants to aim for more customization thats easier for them to do because, well, they can just write the code that way from the start.

So, yeah, as much as I would like to see some more customization myself, they've explained that thats rather difficult because of the fundamentals of the games code - nothing, they can change easly (or probably at all without having to sort of rebuild the game from scratch)