This is possible with ERC-8290. Just drafted last week.
It lets you teleport assets from one privacy protocol to another without unshielding. Protocols that implement it benefit by inheriting the anonymity sets of all other privacy protocols, even existing ones, it imports from.
is anyone working in unifying anonymity sets in heterogeneous systems?
i.e. unifing Tornado Cash, Railgun, Privacy Pools, etc anonymity sets