I’ve said this before in other threads, but I honestly think the steady re-adding of NPCs and features is very much intentional: you’re on a deserted island in the middle of nowhere and you’re steadily building it up over time, so it makes sense that over time, different NPCs are going to be invited along for different reasons, or furniture and clothing is going to be locked behind different stores and upgrades.
Even the NPCs that appear to have been retired have little hints that eventually they’re going to come to your island (Joan’s stated to have bad knees at the moment, Chip has a fishing boat that he goes out in, and Nat apparently travels in search of rare bugs) so, if they’ve got an amiibo, they’re going to be added at some point.
Anyway, in answer to your questions:
1: I want them to bring back these things:
- Re-Tail’s auction house and customisation facilities
- Much more furniture, including the stuff that still hasn’t been brought back from the GameCube version
- Dream Suite
- HHA headquarters type thing where you can redesign villagers houses like in HHD
- Morning Aerobics/Sports Fair (but make the Sports Fair actually interactive this time)
- Fireworks festivals
- Bright Nights (but give it an actual purpose)
- A less obtrusive Nook Lottery
- Post Office for better postal service facilities
- Tortimer Island
- Consoles with mini games on them
- Something similar to Boondox from WW or the lighthouse from GC... just something that involves doing a little task for someone
- More villager dialog and interactions, honestly annoys me we can’t do much for them atm.
- REGION EXCLUSIVE DIALOGUE
- More Nook upgrades, potentially with new furniture
- Harriet with the missing hairstyles and Mii Masks
- Brewster and gyroids
I don’t want them to bring back:
- Excessively mean villagers
- Flea Market, unless it’s similar to the thing where you visit a villager house in NL and you can buy certain bits of their furniture
- NES games (redundant with NSO imo)
2: I’d love it if they added the greenhouse idea somebody mentioned here earlier, and I also like the idea of travelling to other islands for certain NPCs? I’d also like some brand new fruits, like strawberries and pineapples, as well as the ability to make slightly messier paths.
3: if we don’t get another update in the next couple of weeks, I’m gonna say seasonally... until the Hallowe’en-Christmas season comes, then they’ll go back to being monthly. But I’d like them to be monthly?
4: It’s not gonna be the game some people on here seem to want, but it’s going to be much bigger?
5: I’m not entirely sure, but I’m hoping it’s slightly different each time.
6: It’d have to be something like the Octo Expansion in Splatoon 2 rather than something that just mildly expands the game... I’m thinking something like the city from LGTTC, where a load of the other NPCs have shops and where DJ KK does his radio show?