Well. This all got rather hostile pretty quickly. I'm just gonna ignore all that goofiness and try to bring the discussion back on track. I think that pretty much any character below Luigi doesn't really have any chance of winning any serious tournaments, and Luigi is pushing it (oh, and I'd put Yoshi above Luigi, just to mention that). There's a lot of flexibility in the low/mid tier realm, and definitely room for improvement, but aside from MAYBE Young Link, I don't think any of the characters have the potential to break out into what could begin to be considered "viable." At best, He could move up into that upper mid tier category with Ganon, Doc, Mario, DK, etc. So basically, where he is now, only as an accepted mid tier, not a low tier.
As a former Young Link main, I may be a little biased in my assertions, but I do believe that he's the only character out of all the low tiers to get to that point. I think he will excell as an obscure counterpick character for other characters that struggle in floaty matchups, and that's about it.