I guess this is what I'd personally do in terms of structuring a prize pool for seasonal events like this:
- Take all of the public shop hats that have been phased out and lump them into some general pool that can be used across every seasonal event (Halloween's trick or treating, Christmas gifts, etc.)
- Take all prizes from previous years of the event and lump them into another prize pool
- Possibly even take items from previous years' Onett and other common shop releases (not Nexus, Revolution, or Club Crypt) and lump them into another pool
- Make sure to have some standard quota of new prizes introduced each year per each event (something like 10-15 hats, 5-10 furnitures, 1-3 bombs/bows, 1-2 mounts, etc.)
- Throw in fillers like food, gralats, etc.
Combine all that together to create one large and growing prize to compliment the playercount increasing over time. Yeah, people will cry about "BUT MY EXCLUSIVE SHOP AND SEASONAL HATS THAT AREN'T SOLD ANYMORE," but oh well. It'd make the event better for newer players and give older players a chance at collecting the entire prize pool over many years. Everything would still be pretty rare.
It's obviously hard to continue to come up with hats, mounts, and furniture,
especially when themed to a holiday, so this would ease some of the pressure of people expecting 3 pages of hats (like some of us got during Halloween 2013). Stuff like previous Nexus, Revolution, and Club Crypt items should be kept sacred, but everything else could just contribute to a larger pool and a more "fun" event. Quotes around fun because I know 99% only care about how many items they get rather than the actual gameplay of the event.