The only two 'changes' I would make to the 3DS, and they really aren't for the 3DS but for Nintendo in general are
Flash Support for Web Browser
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I still do not have a 3DS, but I've done a little bit of research on the device. Many companies, be they Apple or Ninten or maybe even Sony (not sure) still have not adopted Adobe Flash. Now, said companies also do not have support for a myriad of plugins that are almost must-have for any computer (at least, Windows OS Based). It really pains me to hear that we cannot view YouTube videos on the 3DS simply because it doesn't have support for Flash or other plugins required. All it would take is a little bit of money and an agreement between Nintendo and Adobe, at least for a while. I realize that money always plays a factor in things 'round the world, but Flash has been on PCs for how long? 18 years? And I'm sure Nintendo and several other companies know how many times YouTube is viewed a day by the average user, or have some sort of figure on that. With the addition of YT and Flash to the 3DS, I'm sure it could boost sales at least by a margin, a noticeable one at that.
3rd Party Developer Policy -- Games Need To Be Good
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This is more of a complaint than anything, but if you notice of this generation, 3rd party (meaning, Square Enix, Capcom, Namco, etc) games are starting to recede into small packages where the developer(s) purposefully give you the least content available in order to charge you for DLC (Downloadable Content, e.g ports on the 3DS, that map pack you were gonna buy for Call of Duty, Mercenaries Reunion, among others). Back in the N64 and even the PS2 days, 3rd parties would give you a game of the quality that matched a Zelda or a Halo, they didn't throw you a small mix of things and sell it for full price (
Resident Evil:The Mercenaries 3D)!
The 3DS' game library is already pretty low despite it being (5?) months old, and it only adds insult to injury to have a low count of games that are generally terrible. The only games I honestly see as worth getting at this point in time (that are currently released for the 3DS) are
Dead or Aliveimensions,
Super Street Fighter IV Alpha Omega Edition**, and 'maybe' Zelda:OoT3D. That is only 3 games out of how many? Capcom is probably the worst offender, with their throwing out of ports **(SSF4) and 'bundles' (Resident Evil:Mercenaries 3D) that aren't even done right, and I honestly believe them to have left a bunch of content out on purpose.
You don't see 1st parties doing that, because they have a reputation to be held with their 1st party games. 2nd party developers are oftentimes tied to the 1st party. 3rd party games and their devs are just receding into oblivion, although that's not where they originated. I recall Nintendo saying the 3DS is capable of DLC, but if it is, I want meaningful downloadable content, not a map that *should have* be in the game from launch or a game mode that *could have* been in the game from launch if they but delayed the game one more month. I propose that the 3DS get better 3rd party games while we wait for the 1st party releases, but I don't expect my wants to be fulfilled anytime soon.