I do wish that we got much interesting and longer seasonal events. Honestly for these events I would not even need a storyline at all. Just have a bit fun that would fit with the theme of the event.
The summer one could be different activities at the beach. The halloween one is already better with the haunted mansion but I want them to go further with this.

Just let these events be fun mini games that are not done after 10 minutes. Put the work into the mini games themselves and not into a once done story. Also put every past reward into the game again at that event (like they did at the start of FF14..). People with alts have some nice way to grind these items while newer players wont miss out on them and having to pay real money for it.