Couldn't it be looked at discouraging anchoring? If the majority of charters have no desire to anchor and will only moor and use BB to ensure they get a mooring, then they'll just pick another location for the night to avoid having to anchor. Without BB, they'd show up for FCFS and if there were no balls available, maybe they'd be forced to anchor?

As far as the issue with picking a ball and then finding its not available, maybe a ball needs to be held each time someone gets to the reservation screen. Then you are ensured a ball and then you can then choose which one you want. Still might not get the one you want, but at least you'd have a ball?