Yes, possibly a pause/play button could be added with certain transitions, however not universally, as most effects like Ken Burns, 3D flip, or Book could not react immediately to the pause/play, making it a bad user experience. These transitions cannot be interrupted.
Because I misunderstood the intended function of Bridge, I thought it should behave just like an album, which does have the controls. So, I now think the controls are not necessary.
Without getting too far off topic, it would be useful to be able to "select" a subset of images from an album to be used (fed to?) a bridge on a webpage as a sort of "preview" of the album. That would address both my original concern about the number of items bridge can display and cut down the need to have controls to pause/resume a slideshow or carousel.