First, great work! I think you genuinely understand the style and I love that you stay more within the constraints of the ps1 considering vertices and texture resolution. Always looking forward to your work!
I bought your character pack awhile back and think that you're doing a great job. My criticism of those characters would be the rigs as I know a few more had.
I would like to know if you have any more details for the new universal rig as you call it?
As a Unity developer I'm interested in knowing if this can be imported/created as a humanoid rig?
In the past I had to make a new rig from your characters (in reality simply re-ordering the skeleton hierarchy). I'd hope if this is the case that you'd update your older model's rigs as well, but do understand if that's not the case.
So the rig may look complicated at first but its a 2 layer rig system. The bone groups are organized. The only bones that are exported are the bones in the Game Rig and Physics group (both deform bones).
The other group, Control Rig, controls the Game Rig. The control rig has an exact copy of the Game Rig bones but different hierarchy and extra bones for controllers. The Game Rig has constraints that follow it's copy's movement. The other group is just the Controllers for animating and key framing.
When baking animations only the Game Rig + Physics will be baked. And when exporting the rig, deform only bones will exported. Since the Game Rig uses the Unity hierarchy for rigs it should be considered a humanoid rig.
As for my other models i am still not sure if i will be updating them with the new rig. Ideally I want to but it is going to take time to reanimate and fix the weights for each character.