Videogame development cycles have these things called BUDGETS. Games are developed based around the budget available for the game and the time frame in which the game can be developed.
Hypothetical situation:
Say none of the trophies were ever created. That's hundreds of manhours which did not need to be paid to the artists so there's more money in the budget for other additions to the game.
What could these additions be? More levels, characters, testing for balance...generally anything which would enhance the multiplayer longevity of the game.
Anyone who says, "Oh, there wouldn't have been more characters/levels/balance if they hadn't pissed money away on developing the trophies." is a FOOL who clearly doesn't understand economics. With the time and money saved by not having the artists make these idiotic little trophies, I'm more than willing to bet we could have at LEAST given Ganondorf his own moveset, and that ALONE would have been worth scrapping the trophies.
If you weighted the total time played in SSB Single Player vs. total time played in multiplayer, I think you'll find that multiplayer is ahead by a healthy 200:1 ratio. My SSB cartridge logged over 700 hours of gameplay on it before we switched to melee. How often do you think single player was played after all the crap was unlocked? That's right: it WASN'T.
The trophies add NOTHING to the multiplayer gameplay. NOTHING. No one buys SSB so they can play it alone (unless so they can practice and get better against other players, something which happens better in vs. matches than "break the targets" mini-games).
What is the fascination with ensuring that EVERY game has a single player mode? World of Warcraft is probably the most successful MMORPG in the world, and it DOESN'T HAVE A SINGLE PLAYER MODE!!!!! WHOAMG!!!!!!!! You can't even PLAY the damn game OFFline!
SSB should be the BEST MULTIPLAYER EXPERIENCE THAT IT CAN BE. Want a single player experience on the Rev? Buy Twilight Princess, Mario 128, Red Steel, or any of the other dozens of games which are dedicated to offering an excellent single player experience.
SSB: Rev needs to be the BEST multiplayer game that it can be, ever, and if SSB: Rev has clones with textures that don't connect, Ganondorf doesn't have at least ONE goddamn bladed weapon, and there are over a thousand trophies to collect, then someone at HAL Labs needs to commit seppuko because they f*cking FAILED.
AI that learns is a good idea because it's the closest that someone with no online connection has to playing against opponents which will mimic human players. Beyond that, HAL can work on the single player aspect only after the multiplayer is so good it puts the game in the running for GOTY.
Halo outsold SSBM. A brand new franchise on a brand new console beat Nintendo's tried and tested franchise with a huge following.
SSB: Rev is going to be Nintendo's FLAGSHIP multiplayer WIFI title. If someone is going to buy a Rev to go online, this game is going to be the primary reason. This game NEEDS to kick ass and take NAMES in the multiplayer department, and if that means slacking on the single player offering, so be it.