There really needs to be a shortcut key for switching timebase between Seconds and Bars. You could then create a macro that selects all tracks and toggles timebase to seconds (if you are aligning the grid to your music) or beats (to stretch your music). For anyone who does tempo mapping you'll know exactly why this is necessary. For example, say you just added a tempo node and the last measure you tempo mapped was wildly out of time with the rest of your song. You could toggle every track to timebase->bars, stretch it back up or down into a more reasonable tempo then quickly switch back to timebase->seconds and get back to tempo mapping.
