Supporting retime (speed change) for clips in the timeline is needed for any serious conform and prep work. Including non-linear speed changes. Generation is nicely scriptable, but if I can't conform and check timeline, I can't really prepare Fusion comps in it. This degrades Generation to smart playback/versioning tool.
I do believe that having multilayer timeline would helped a lot for Generation to be a conform tool that is able to prepare / create Fusion comps for artists. We have very few jobs with only one plate those days, and trying to use version stack for prepping comps is a nightmare.