Do think of underfloor drains. They are your friend.
Floor drains are good.
Anti-backflow valves, and floor sink traps are mandatory. Automatic trap primers seem to lead to flooding. For example, St. Louis County recently opened a new jail. However it was delayed three months because the week before opening when they discovered if all the toilets were flushed at the same time on the eighth floor, as prisoners are known to do, the sinks exploded on the bottom floor. The plumbing designer had followed normal industry practice for commercial buildings, but forgot jails house a user population that is different from a normal commercial building.