I have another idea for a huge EP (like it would prbably be the biggest EP ever)
Combine seasons, pets and farming.
Have seasons and everything and put in farming because that would go hand in hand with the seasons. Would be so cool if there was an big land side neighbourhood with a big farm. Imagine you could have animals like pigs, cows, chickens. Add in cats, Dogs, rabbits and maybe horses to have on your farm or at home (no horses at home tho. That was a mess in ts3)
It would fit so well together and may be the most critically acclaimed one because if actual Content that's worth the price.
Besides the country side theres also a more downtown like neighbourhood with cafe's, Restaurants, ... to go for a walk (with your umbrella when it's raining.
A big forest like neighbourhood with a park (playground, bbq, dog playground stuff, cat toy stuff,...) lot, a big lake that freezes in winter so it's the absolute hot spot for families, teen Groups and so on to go ice skating. Have wild animals like rabbits hop around the forest, bird feeding places, maybe deer feeding.
A residetial neighbourhood or two where it's more like the other worlds.
Have seasonal holydays like NYE (with firworks at 0:00, Christmas, thanksgiving, easter, maybe something like a Parade that's once a year (carnival Parade through the neighbourhood (I could see that crashing the game tho

It would be so cool tho)