The roleplay sim I belong to currently uses a "hack" to do this - we use RLV to route chat messages through an object, then use scripts to change the object's names so the person's speech comes out via the object. We have a lot of fun with this - if someone gets petrified and (temporarily) becomes a statue, they tend to enjoy having their name changed too.

An official way to change display names temporarily as part of an experience would be fantastic. It doesn't need to be persistent (e.g. current session) and having it part of the viewer would allow the person's username and other details to also be shown.

It's worth considering Discord already works this way with per-channel customized names.