I would suggest that, 'specially if you go modular and have lots of scouts carrying a part of your FAK, that you develop some type of easily opened yet secure system to seal each module, so that you can easily tell if it has been opened. Zip ties probably won't work, too time consuming to open if you need access NOW. Possibly tape zipper tabs together with "evidence tape," which can be purchased from a law enforcement source like Galls (galls.com, search for evidence tape). That way you will know if some nosey person has been digging through a module, possibly removing some vital piece of equipment.

ps: I don't own Galls, but have purchased from them many times with great service...