Feature request: Ability to add custom type visitors

[AllTaken]

It would be very nice to be able to add a custom visitor, for when you have a custom type, that needs special processing, or for fixing/working around issues before a new release with a new type visitor is released.

And maybe even, being able to override an existing type visitor.

[j-mok]

Has there been any movement on this one? I could too use something like that, specifically to make DecimalTypeVisitor emit data format as decimal instead of 'double' (or replace this particular visitor altogether). I couldn't find any reasonable extension point to do it...