I'd like to see the introduction of the Springfield Costume Shop
https://vignette.wikia.nocookie.net/simpsons/images/4/49/Springfield_Costume_Shop.png/revision/latest?cb=20130604194355
Ideally, it should be a freebie at the beginning of the event. When tapped it'll take you to an event screen or directly to the store where you can purchase a slew of skins from Tapped Out's inventory so you can have as many characters as possible dressed up for Halloween.
Through the costume shop, you should be able to earn new freemium skins and purchase old and new premium skins as well.
In addition to stocking all the normally available Halloween skins, it would be a chance to bring back seldom seen old skins like Beer Stein Wiggum, Homer Barbarian, Bartman, Mayan Homer (for people who have been clamoring for him), Archer Lisa, Bouncing Battle Baby, U.B.O., Shredded Ned, Football Nelson, etc. etc.