There are third-party applications that can do this kind of dayparting for you. They are based on the Google AdWords API. If you can figure out the API sample code (see [google.com...] ), craft some simple php, and install a cron script, you might be able to do it yourself.
It can either be built into an API or you can use macros.
Frankly though it does far more harm to daypart Google than it would to leave it on all the time. Imagine it being like a queue at an all you can eat buffet. If you decide not to queue any more (i.e. switch off) then you have to get back in the queue and watch while others fill themselves.
I didn't get the analogy to the buffet. You can turn off any campaign whenever you want and turn it on whenever. So what kind of queueing are we talking off here. Care to explain it in greater detail so that I can understand?
You dont go to the back of the queue when you pause and restart your campaigns, the only reason things will have changed will be if someone new has started advertising while you have paused, or changed their bids etc. Adwordsadvisor confirmed this recently in another thread. So you can pause and unpause manually with no ill effects in terms of history and position.