> [...]

This is too complicated that I can fully understand just from reading.
I would love to see a screencast of the thing in action debugging a
real-world example ...

> First, I would like to only press the traceBug button once.
> This means that once the debugger is brought up traceBug needs to be
> restarted
> so that it can cause the second debugger to come up.
> Obviously this can be done but I don't know how to do it.

You can avoid restarting the calculation by capturing a (or multiple)
continuation(s) at the right place(s). Then you can resume from that
point anytime, open a debugger, etc.

HTH,
Lukas

-- 
Lukas Renggli
http://www.lukas-renggli.ch