Kinda reminds me a little of HHN Orlando 2012 where the entire park was a cemetery unearthed beneath the park (minimal set pieces spread through-out, including tributes to former rides/attractions) and you had the roaming "Legions" (vampires, trick r treaters, warriors, chainsaws, zombies, etc) it wasn't the best, but it worked.
I feel like this concept could work for Hollywood, but only if they made the effort to cast enough scareactors to fill the streets. Although, French Street should remain as a fixed SZ. Also we'd definitely need a set of scareactors for the Lower Lot.
Pull an Orlando, give us Graveyard set pieces (we all know they have an excessive amount)... just decorate the park in traditional spooky Halloween/Fall decor & unleash the the terrors of Horror Nights past. You could even have two sets of casts, but not duplicates, so you could pass through an area twice but be stalked by different monsters than the previous.
oh yea.... speaking of anniversary ideas. Bring back the Creature musical but put it in Waterworld!! A Ragin', Rockin', Epic Stuntacular that'll be a splash hit! *hides*