Support for four GamePads at once.

Splatoon will be more fun that way.

I would also say:
- Lets you play Blue-ray movies (i dont know if they can), and it lets you watch on the gamepad, if someone is using the TV.

- Lets you design your homescreen interface (both the top screen and on bottom screen). Like put furnitures and stuff (the miis will sit than stand) and put those game releated stuff.

- Maybe use the mic on gamepad to access stuff like the xbox one (again i dont know if they can do this lol)

And i agree with all you've said, especially the achievements.

more games
thats all a console really needs

YES YES AND YES!

and they can update games that have released to let you use more than one.

Invite system, unified account system and leverage Virtual Console for Pete's sake!

The other ideas I either don't care about or actually don't want. I suppose I could deal a unified gamer score/achievements system provided it was not mandatory in every game (I'd rather my developers focus on the core experience) and you could simply turn it off at the system level.

The ability to play 3rd party games!

I am very conflicted with a trophy system. I like the idea of keeping a record of achievements but many of them are really stupid. I have gone out of my way to platinum a few games and thinking about it makes me sick lol.

In saying that, why not have a Nintendo Stamp Book.

Like all the stamps you get from Mario Kart 8 and 3D World would be collected in it.

My list:

1. Achievements. Yup, I like em. I didn't' think I would, but I do. They are great in Xenoblade as well, but would be better if they were part of a system-wide collection. People like to collect.

2. Customization home screen. Miis' running around is cool, but some different themes would be great. Maybe that Zelda U scene for a background with Zelda sound effects when you click on things. Or a SM3DW theme. Or a creepy Metroid one. Or just a different look for a generic Wii U system. There should be options. People like to customize.

3. A far better classic games system. Wii's Virtual Console was an industry leader. Wii U's lags far behind. There should be a fantastic, easy to navigate classic game library where you can find and play them all. They should also have a team remastering them all with new visuals, sound and presentation. It could all be part of a subscription service where you get the whole catalog for a small monthly or annual fee.

4. A more searchable eshop.

5. A redesign. This is different than the others, but a smaller, cooler gamepad would be better, and a new aesthetic for the system would be cool. I like what they are doing with the N3DS. They should channel some NES or SNES in the look of Wii U.

This is exactly the kind of thing I'd like to see if Nintendo were to implement an "achievement" system.

Sounds like Sensible additions. I would personally like to see more demos aswell. It would be good if they didnt have a 30 use lock aswell. I never use it up, but it just forces me not to play and eventually forget completely about that game. I dont think its useful at all.