If you're able to ditch the meeting at Hilton Tokyo Bay, then stay instead in a hotel room that overlooks the trains. Hotel Metropolitan Marunouchi and Century Southern Towers (Shinjuku) both overlook huge train stations and you can spend a long time watching trains pull in and out. Plus you won't have to do that crazy train transfer between NEx/shinkansen and Keiyo line and then stay out of the way in Maihama.