Yus, that demo came out just in the last few days, I believe.
Haven't had a chance to play it just yet, since all the space on my N-card is occupied right now.
So, As far as specifics, I will take the lead in setting up guidelines, basic ones at that.
Oct 8 '08
Features:
*I recommend keeping most if not all of the mechanics introduced in brawl that were not in direct control of the user, such as Lucario's Aura ability mods that were based on his current damage ( As well as his Score Position in the battle, FYI ). Of course, adjustments will be needed for characters not in the roster that would leave gaps.
Characters(And Adjustments):
Mario
Luigi
Link
Samus
Pikachu
Ness
Capt Falcon
Donkey Kong
JigglyPuff
Yoshi
Fox
Kirby
^ As you can see, the SSB Veterans are all still there ^
For Non-vet characters, that either haven't been in yet or are in brawl or were in Melee, adjustments should be made to match those that were in both Melee and Brawl.
Non-Vet Characters:
Marth < Would Retain the new Dancing Blade and the new Shieldbreaker.
Roy < Has a Dancing Blade that works more like the Melee One, just not as strict on it's timing
Ike < ... Not sure what to do with him yet
Mewtwo < He should be fine as he is for the moment.
Falco < Slight Adjustments to some of his timings to make him more like the Melee Version
Kirby < Some Items should be allowed to give him powers from the actual kirby games.
^ The direction should be apparent for now ^
New Character Suggestions:
... It should be reasonable. Not just totally 'cool' characters, as well as not totally 'funny' characters. a bit of both is perfect.
And also should most likely have made an original appearance on a nintendo console.
Example: If you are going to go for a Final Fantasy Character, Cloud Strife is probably Pushing it, though I think Cloud is a pretty damn deep character, I'd more recommend Locke or Terra in his place, since they were in FFVI, which was on the SNES.
Conversely, characters that have a renovation somewhere down the line that may have ended up on another console are possible.
Anime and Manga Characters... though I'd hate to say it like this ... should be more or less excluded. Believe me, I am an Otaku, I know for a fact that this will bring much pain and torment to Players. The Naruto and Bleach fans would have it out in spades. (First-hand account from a witness)
Some Starter Recommendations would be:
Guy (Fire Emblem GBA, I think it's 6 or 7, whichever has Eliwood, Lyn, and Hector) < I'd suggest for him, he'd have quick glancing attacks like Metaknight, but would be more like Roy in terms of agility.
^ Thats all I decided for ^
EDIT: As a note, these should be the stock settings and characters that would be included to demonstrate the stock features. since it's open source, people can do what they want, but it's a push in a direction I think.