I'd like things that are practical, yet plausible at the same time. I see how the backpack could work (and think it's a good idea), but I just don't think it really fits in an AC game. They may as well just give you extra storage space in your pockets and ditch the idea for the backpack. It'd just make the character too bulky. And then things like the ability to cook, grow vegetables etc... No thanks. That's too similar to The Sims (though I would like to see red turnips return).
Something I had wanted in CF - which was possible with the weather channel - was the possibility to sync the two, so the game would mimic the weather that was forecast in your area that day. Though looking back, I can see how impractical that really is, as it would suck for people who lived in remote areas where it never rained/snowed, and would probably be a horrible idea.
As for ideas that I could see being in the game, or at least have a decent chance... I wouldn't mind seeing the addition of creating custom skirts (possibly socks), which I think is a given anyway. The ability to rotate Public Works Projects would be nice, but I didn't really care about them that much in New Leaf (maybe that was because of what I explain the last paragraph), so if you can, cool, if not, also cool. Bronze tools would be nice, too, considering we already have gold and silver, but I doubt they'd happen so... I'd also like to see levelled towns make a return, like in City Folk. I really disliked having a flat town in New Leaf, though I can see why they did that, due to the elevation between the land and beach, another level would've made the town seem like a mountainous region, instead of a remote area or whatever. And as previously mentioned, the home design feature from Happy Home Designer is inevitably going to make an appearance in this game, and I'd be shocked if it didn't.
As for actual features and not just additions to pre-existing features... I wouldn't mind seeing the island get a revamp, with more things to actually do there. Something I speculated in New Leaf, before diving creatures were actually confirmed (as in, the trailer where you just saw a player dive, but you never see what they get), I wanted it to be a treasure chest of some sort, which you would give to Pascal, who lived on the island, and he'd give you a part of a new sunken treasure kind of item set, which could only be obtained this way - similar to the pirate set from the scallop. Of course, the scallop would still work the same way too, except it would give you the old pirate set. Mining is something people have wanted for a while, and I'm still curious as to what that cave was for on the prototype map for New Leaf, and if it really was a feature that got scrapped, and will make an appearance in the next game. Whether it was mining, or a new area to fish in, or something entirely different, I'd love to see caves make an appearance.
That said though, the only thing I really want is the ability to determine where villagers put their houses, or at least the sign post system from the old games to return. The one thing that really bugged me about New Leaf, and hindered my gameplay, was the fact villagers could literally place their houses anywhere. Customization is one of the biggest aspects of the AC franchise, and I felt this addition really killed a large part of that. I was resistant to landscape and design my town, because I didn't want to spend weeks on end designing an area, only to have some villager place their house in the spot I was working on the day after I finished. Yes, I could plot reset, but I really don't have hours on end to spare to plot reset for villager houses, when the old system of where they would/could move in in the older games was fine. I don't really care about the whole "I want X villager to place their house in Y spot" fiasco, I just want to have the ability to determine where villagers can place their houses, so I don't have to be hesitant to landscape my town, or have the sign posts return.
