It's a great feature, and there's so many ways they could improve and expand on it that it's hard to name them all.

Besides just more appearance options and portrait slots which are a given, some things I'd like to see:
- More control over the information on the plate (e.g. being able to hide some of the currently displayed information, and choices for other things to display instead e.g. job levels, mount/minion/card collections, favourite mount/minion/orchestrion roll, top 3-5 jobs, etc, etc)
- Being able to save multiple plate setups and switch between them automatically with gearset links
- Portraits showing up in more content (maybe optionally)
- More possible poses for portraits including job actions, or at least the battle stance/victory pose emotes

As for problems, there's a lot of bugs with portrait creation which I guess is to be expected as a beta version. As most have discovered the face detection requirement is pretty wonky and it's not that hard to make a portrait where the character's face is not visible at all. An understandable restriction but still a bit of a shame for me who just wanted to make some cool ones. I'm also curious to see if and how the blatantly erotic portraits might be moderated.

I'm also not sure if portraits being automatically unlinked when the associated gearset is updated is meant to be the final design of that feature, because it's really annoying. It'd be much nicer if updating a gearset could also simply update the associated portrait. And even that's only because the current portrait system can't save a gear appearance for more than one portrait. Ideally every portrait would simply show the gear you were wearing when it was saved, or could optionally be set to always reflect your current appearance.