I'd like to see:
An extended quest where you go up against Lewis in the mayor elections (maybe post-perfection)
If Pierre's at the resort, Jodi and Caroline step in to mind the shop
If Pam's at the resort, Kent drives the bus to Calico
Sandy to appear in the valley on Emily's birthday
Some form of annual event with the town in the community centre
I strongly disagree with the player going up against Lewis in elections, as I like to pretend that he does work. If we become mayor it would become our responsibility. Forcing the player's hand in doing specific work would impact the vibe of the game I am against it. HOWEVER, I would like to see other characters go up against him in elections. Maybe our spouse? Though it would be awkward if we were to divorce them lol.
I really like the rest of your suggestions, to add a few similar;
Have someone work at Clint's on Fridays or when he is at the resort.
Have Leah work at the Carpenters when Robin is away on Tuesdays or at the resort.
Have Emily work the bar when Gus is at the resort.
In general I really like the idea of younger characters stepping up and working when others are not available.
Personal additions to the game;
Something should be done about the kids' education. Maybe there should be some dialogue about how they have to take standardized tests or other proof that they are learning. This has always bothered me. Is anyone double-checking that Penny is a good teacher? She does not seem qualified to me. I tend to avoid her when she teaches because it leaves a bad taste in my mouth.
I would like a storage organization system for decorations. I have multiple big chests of random stuff I accumulated in my playthrough. It's hard to find the stuff that I'm interested in when decorating, and I don't want to get rid of it until I get the corresponding furniture catalogue for each item because I don't know what is one-of-a-kind and what is generic. Maybe a generic "furniture catalogue" similar in function to the wardrobe would be helpful.