> I think we're starting to talk past each other and this is falling into the well-rehashed pit of "are runtime types really 'types' or just semantically normal runtime assertions."

Sorry, that wasn't the direction I was trying to go. I just meant to say that the work it'd take to make different type system in a dynamic language is approximately the amount of work it'd take to make a whole new language.

So I think from a practical POV, it's fair to think of the type system that comes with a given dynamic language as being more or less intrinsic to it, regardless of what one's philosophical stance is on types in dynamic languages generally.