Modular Character (Pawn) using Skeletal Mesh Merge is what I’d shoot for out of the gate. This doesn’t swap out the actual class so there’s no loss of current movement. It’s all data driven (Cosmetics Struct RepNotify).
You’d RPC the Server to change “cosmetics” it’ll set the struct elements then execute the OnRep function. Handle all the skeletal mesh, static mesh, materials, VFX in the onrep function.
Use Actor Components to handle changes in movement logic and input.