When I played MP2 on the GC I tried to finish it with the aim of scanning every single item, enemy and upgrade found in the game and collecting every single possible upgrade. So far when I beat the bosses at the end of the game I had a total of 81% and I saw a clip at the end of the game which showed Samus removing her suit - looked exactly like the pic of zero suit samus in SSBB lol.
btw When I get the time ill try to finish it with 100% total so i can see the mother brain reform herself as dark samus (havent seen it not even on the net!)
I reckon having an alternate character for samus in SSBB is a great idea. In SSBM one of the best characters to have in the game is Shiek (alter ego of Zelda), alongside with Fox and Marth - been looking at the SSBM tornament sites lately. So yeah I hope having an alternate character for Samus will balance her long range attacks with short range attacks. Not to say in SSBM that her short range attacks are okay but they could do with more power (like Link who has less powerful long range attacks and better short range attacks)