[Donut]

I don't think downtime is going to really be removed by that; sure some robots will start later, but you still have 15 or 20 seconds for the whole autonomous to run (and forcing teams to announce what they will be doing before autonomous will give away their goal, not something I want my opponent to know for their defensive autonomous).

If you keep them the same time then the difficult tasks are more difficult because it's more to do in the same time; by increasing the time for harder tasks you remove a large part of the difficulty from them (time is usually the biggest problem in autonomous mode).