I have some patches that work with (trace) and backtrace that provide "advice" to the facility on a per-frame basis for how to represent long arguments/results based on the name of the function for that frame.
 
This matters a lot for QPX since we use a lot of packed integers to encode things in one argument. It's nice if (back)tracing can decode arguments properly rather than having to resort to editing the function to insert a format string "I'm being called with..." and because setting *print-length* is not enough to stop printing a 50,000-element bit-vector or a 1MB string, both examples occurring in real life for us.

If that sounds nice, I can make it work for generalized function names which it doesn't, just based on how it represents the advice presently.