I would like Kapp'n to sail the boat that takes you to places over the sea like the houses on stilts (you see it on the map) and the island. Either that or you can swim there (but I have a feeling that in the game there will be a boundary of where you can swim - What if you try to swim for eternity on the opposite direction of the island?). Maybe you can catch fish on the boat that could not be caught at the beach. I mean, would you really find a shark right next to the sand, at the edge of the water? Maybe some spots are better than others - like the rumoured 'good spots' told by the neighbours in the past games.
For the train I would like what was in the old game- the monkey conductor sounds cool. Maybe Rover can every so often sit down next to you and have a conversation. I hated how you only got to see him twice at the bus in CF and after that you had to have the same conversation with the bus driver. I was thinking maybe in AC there could be more episodes to complete - a series of events that happens when you talk to people in the right order - so maybe talking to Rover for a certain period of time starts an episode. Even better yet, you can choose who you can sit next to in the train, so you can talk to different people and different things happen.
I would also like to see him every so often at the cafe and I loved Garrett x50 cal 's idea about Rover asking questions at the start for being a mayor. Maybe that decides what you look like (eyes, hair, clothes) and is set out like an interview (but whatever answer you say, you still get the job - Rover says after the interview = I love how you're so sweet - you will get many people to sign contracts with you since you are so likeable and you know, if your people of your town likes you, you will have a happy town, or: I like how you have so much energy and fire in you - I just know I will be handing it to the right person if I choose you - you are so confident and strong minded and that makes a great mayor, etc). I just thought of an idea. Maybe Tortimer says he is growing old and that he needs a vacation - to retire and so he gives you an interview to see if you are good enough for the job.
Lots of love,
Cherrypie