I am wondering if there is any way to make a player-controlled character translucent/transparent within Unreal Engine 5.1. The best example I can give of what I am thinking of is the game Super Punch-Out for the SNES.
Create a material with full translucency. You could easily have a material with a single 0 to the opacity node.
If your character is using many skeletal meshes (clothes over a base character) then look into using the dither material node. It will skip transparency sorting and not reveal the insides of your character. It also has a flat cost in terms of performance.