Whenever I design anything, I end up restarting from scratch - sometimes dozens of times.
Start, build into a corner, realize I should have done X but didn't see it when I started, restart, repeat.
You couldn't do away with that entirely, but one of the best possible uses of the timeline is to roll back the clock and bake in knowledge of what's coming next.
Done well, that would lead to much more elegant designs with less complexity, smaller part counts, and easier assembly.
This is more of an abstract concept than a fully fleshed out idea, but replacing the timeline with more of a dependency graph that lets users do surgery / refactoring seems like a great start.
