Although I think aiming for building this into the general programmer's development environment is ideal, there is an easier first step. Simplify and reduce the scope of the project to where you build this into a pedagogical programming environment. Most programmers have solidified these mental models into their heads. We only need to see them when we've made an error. Students, on the other hand, are flying blind and need this visualization desperately. More than that, the types of programs students build are highly constrained assignments which are more amenable to visualization.
people are starting to play with interesting techniques for augmenting programming like: