I just had this flash of insight...

A visual trace debugger could (probably, by someone more skilled than I) easily be programmed for PD. It would have the ability to trace through a patch as it executes...in real time or in slow motion. This would allow you to see how convoluted your control structures acutually are. I know PD can process multiple things at the same time...to get around this "pulses" of control flow would have to be used and you would end up with something like christmas lights blinking in a row.