Spire or Weavel. Not because they're both my favorites, but because they have such good stories to be explored. Spire's is obvious, and it would be great learning just how Samus decimated Weavel.
I agree about Kanden, he's a good character to focus on, too. I wouldn't choose him over Spire or Weavel, though.
Sylux is all but inevitable. His story blatantly screams, "MARKETING TOOL." Mysterious hatred, unknown species, unknown weapons.....Nintendo could pull it off, but he's so incredibly cliché that it would take a lot to impress me ._.
~*CB*~
The 8th Champion