At Facebook they actually do hot code swapping of Haskell, which is a statically typed language.
The rules they follow is that the swapped in object code must export functions of the same type as the previous version. There is nothing checking these types are correct other than human testing, so it’s effectively dynamically typed at this point.
Alternatively we could define an opaque “any” type and force the user to safely decode their data on code change. This isn’t an option for Haskell as their runtime needs to know the memory layout of the data as it is not designed for dynamic data.
I could imagine a system like this working for a typed Erlang. If I might self publicise a little, I’m working on a typed language for the Erlang VM at the moment, and I plan to experiment with this here 
GitHub - gleam-lang/gleam: ⭐️ A friendly language for building type-safe, scalable systems! · GitHub
For more info on the work at Facebook the keynote from Simon Marlow at this year’s Haskell exchange was very informative.
