I tried pharo, its an interesting thing but I don't see it as a particularly practical solution.

Yes its editable in runtime, but not the whole thing and not reliably so: I remember changing some low level array methods that broke the whole image.

Even in pharo your data has to be organised in some way and if you add new code to existing image you have to know how to reach the data you need.

And the biggest downside to productivity and stability is it doesn't have a type system and every action can fail because the receiver doesn't support a particular message.