As much as I want an online Pok?mon game, I find a complication rather hard to solve...
First, think of the world of Pok?mon. See how large it is? Now wait a few years to see how much larger the Pok?mon gets. It's a lot, isn't it? Assuming that Nintendo and Game Freak want to keep the game up to date, I find it hard for them to expand on a console. All good MMORPGs continue to evolve as time progresses, and console MMORPGs can only go as far as the game data contained on their disks (or cartridges. who knows, maybe they'll have a comeback!) That's why FFXI failed for the PS2 (that problem as well as making the redesigned PS2 NOT able to use the provided hard drive. wow, that's smarts, Sony!). Phantasy Star Online Episodes I, II, III, & IV (for ALL of the sysytems) could have been worthwhile had Sega prevented hackers from roaming free on their servers...
If a Pok?mon game were to succeed online, there'd have to be additions every once in a while. Just like Ultima Online, the first MMORPG to have existed, is still running strong: expansion. I don't think consoles will cut it yet...
Until now, I believed that the creators of Nintendo resented the online concept. Now that they see the potential, I hope they don't screw it up with the Revolution.
Oh well. Enough of the bad stuff! I would love the online game to include each and every single detail found in the games and show (it seems that the anime is more directly linked to the games than the mangas). Players would be trainers who could start out in any town or city they wanted. (If Nintendo and Game Freak are inventive enough, they can figure out how to make a house for each player.) Of course, before leaving the town or city, the player would choose between the three starters that are from their region.
I'd also like to be able to completely customize my trainer, from looks to personality. The house would be a nice thing to customize as well. If players wanted, they can also change how their Pok?mon look, like adding a mohawk or something.
The battle system would have to be completely re-vamped though since we've seen enough of the 3D "battles" on GameCube and Nintendo 64. I'm thinking real-time battling, keeping the camera behind the player's Pok?mon. If the battles were to be like the show's, they'd have to add something like Stamina for Pok?mon since they'd be running around the battlefield, not just standing there, taking hits like a tree, or miraculously missing a Pok?mon that's standing still. It'd be cool to see the Pok?mon interact with their environment, using boulders as cover or something to bounce off of.
Man, I have so many details I'd like to add, but I feel like this post is long enough already...