Probably the simplest way to 'start' and 'stop' is to 'Pause' and 'Resume'. You can Pause and Resume entire campaigns, or individual Ad Groups - whichever best suits you.
One note about pausing: because statistics can be delivered to your account up to three hours after they occur, you will see clicks and impressions continue to accrue after you have paused. Never fear, these are click and impressions that occurred before you paused. However, they appear afterwards because of the server delays.
Please know that advertiser feedback is taken very seriously at AdWords, and you can always make suggestion by writing to adwords-feedback@google.com.
I have also gotten in the habit of forwarding suggestions posted at the WebmasterWorld thread (hint, hint) below:
Thanks!