Would it be possible to implement MIDI/OSC/socket/websocket listener to control selected avatar sliders/spinners/2D puppets from external sources? Avatars 3.0 give a lot of freedom, with that it could be extended to experiment with more interesting wearable devices, which could animate your avatar.

For example someone could write an app for eyetracking to be mapped to 2D puppet controlling eye position. I have little diy heart rate monitor I could use it to animate a little heart on my avatar with sound, I think it could be pretty neat.

Additional body tracking points might be possible, mouth tracking with external cameras and self written software could be used.

Small effort of enabling external control feeding on your side would give you so much "free" features made by users, which would be happy to make a lot of creative fun weirdness.