The weekly sign off idea might be a good one if the 200hr cap doesn't work for us this season. It's a lot of paperwork but would be a good alternative.
I do like one aspect about the cap being known upfront... that student leaders need to learn delegation skills and make sure other members in their departments are fully trained so they can take over more of the load.
Our team has a very full fall schedule building multiple robots for a pre-season game, the
BunnyBot Competition. We use this as a training time for new members or those switching departments. It takes on new importance with the new time caps as it's our best opportunity to make sure everyone can contribute fully during the build season.