Swappable argument serialization (eg pickle)

[RealOrangeOne]

Currently, arguments and return-values must be JSON serializable (using the default json encoder / decoder). This avoids a number of potential issues, at the detriment of flexibility.

Should this be something configurable? And if so, what are the most useful options (eg pickle, custom JSON encoder / decoder etc).

[zbyte64]

Would be nice to support pydantic models as well, though there's a difference between serialization (objects to primitives) and rendering (JSON or Pickle) so I am not sure if that should be handled separately.