Perhaps fencing is the answer (no not buying/selling stolen goods -- nor I am I suggesting running them thru with my steel). Convert one side to a little off-leash dog park. Fence another side off for the kiddies so parents don't have to worry about them running into the street or getting nabbed. I suspect that people who aren't so well intentioned would be less likely to cross a hard fence line, and if there are people undertaking more nefarious activities they wouldn't want to be stuck without a good line of escape should an authority figure show up.
I'm certain that I've seen drug deals/use occur behind that electrical box. Generally the non-skater kids and the older bums. One way or another you've got to get rid of good hiding spots in public places. Unfortunately the comfort level of Ballard Commons, combined with a bit of secluded space & wide open access makes a perfect combo for undesirables.
