I wonder about Solid Snake, seeing as how he was in SSBB and the MGS creator still wants Snake in the next game.
The system itself doesn't interest me so much on this idea of Specials are the primary way to get kills, because they can still be killed by a certain number of damage. Without any kind of health system, this just feels like random occurrences of "oh I just died". It also seemed like the characters really didn't have differences to them besides "bigger guys move slower". They were talking about one character being all about laying mines and being more ranged, and that same character was just bashing opponents melee style with no issue.
They also do not seems to have much variety to the levels besides what's behind them. The game doesn't need to be all SSB and have edges or anything but just a lower level with some middle level platforms isn't going to work well for game that employ double or even triple jump abilities.