In the long run, what Renoise needs, and will eventually get, is a way to work with “clips” - a.k.a. re-usable content.
I’ve suggested a simple way to get it working (part of the zoomable editor feature proposal), which would, for instance, allow you to create an 6-note long sequence, and have it playing next to an 8-note sequence (3/4 & 4/4 polyrhytmic figure)
What is beautiful about the 2.0 release - which have happened since I wrote the feature proposal - is that the new delay parameter makes it much easier to work with rhythmic material. IMHO we don’t need different speeds for each element in the song anymore. We DO need better squash and stretch tools, however!