I have been seeing a lot of requests for JTAG pic chips and other use cases.
It has struck me that if you are doing general work on some of these that using a dedicated tool for the job and not trying to use the swiss army knife.
So support in buspirate maybe should be minimal, to handle timing critical items and then let external tools handle the larger more specific device activity. At least initially.
In following that chain of thought I wonder whether part of the binary mode should allow a download of a few instructions for one of the PIO channels and then act as an interface between the external device and the pins. So when someone wants to interface to something else with a timing critical loop, the bp5 handles the timing critical bit stream and the external tool handles the non timing critical byte stream.
I am aware from another post that Ian has identified there are resource limits on the PIO .