Mmm, looks like a combination of the waveform editor’s transient detection and the “slices to pattern” tool could handle this exact thing.
Transient detection:http://tutorials.renoise.com/wiki/Waveform#Slice_Markers
Slices to pattern:https://forum.renoise.com/t/new-tool-2-7-2-8-slices-to-pattern/31593