If your goal is only to isolate work so it can crash independently then indeed distributed actors is a nice way to achieve it but the cluster library may be a bit over an overkill for it -- it'll actually bind network resources etc.
There indeed have been attempts to work on this!
The most recent thread was: Runtime extensibility via distributed actors - #22 by mlienert and @mlienert did a great job with his GitHub - martiall/swift-subprocess-distributedactors over there.
It uses sub-processes and/or wasm to isolate workers which then could be allowed to crash in isolation etc. Please check it out and maybe we can collaborate on pushing that lib to "completion" from its prototype status? 
PS: I would love to kickstart some form of "Distributed Actors Office Hours" soon so we could get together and push these things to completion, from just "proof of concepts" of which we have a lot... Maybe in the new year! FYI @jaleel