Eh. I personally tend towards the desire to see races that are aesthetically-pleasing added. They need to be different enough so as to seem exotic and not end up feeling boring, but monstrous/ugly = bleh...
Being a huge fan of PSO, I'd of course like some sort of 'synthetic' race a la the CASTs

However, that's probably a bit too out there for the current state of Hydaelyn, so a design more based off of Mammets, but made more humanoid could work.
Kind of like a cute, Robo-Taokaka or something.

Or something a bit more eerie in nature. As I've said before, I'd like something sort of etherial, spindly, and alien-looking. Maybe with sullen or 'missing' eyes, partially luminescent skin, etc.
And perhaps with long claws instead of fingers
(a la the succubi we've already seen

[or a less deformed version of Eve's hands from Parasite Eve]) and with incredibly long/lanky arms and legs.