Introspective, live languages.

I'm planning to build an interactive development system, very similar to Smalltalk. It seems that all implementations of Smalltalk, except Squeak and Pharo are dormant or abandoned. I'm not sure either of those fit my needs, although the VM may, as I'm looking for a starting point from which to build something. I'm not precious about Smalltalk, so looking to see if anyone knows of any other options. Primary feature requirement is the image based, live environment, in which you can make changes to the entire environment live while it is running. Full introspection is imperative too, so the user can open up objects and inspect/change their behaviour, but that sort of goes hand in hand with the previous requirement.

Any pointers appreciated.