Why? Because he's not someone you like? Or another reason?
1. What do I seem awfully confident about? "Brave" not being Agumon? Yeah I'm confident in that, especially when Erdrick and Yuri fit in with that better, as the word "Brave" is related to their characters in a similar way to how "Jack" is related to Joker. It's like an analogy or a word puzzle. Having one item with the word brave (one that's used by an evolution and not even the original character) is too far off to likely fit, unless you want to say someone like Finn from Fire Emblem could be "Brave" because he prominently uses a Brave Lance. Agumon would likely have a code like "Digi" or "Tama," not "Brave."
2. Veterans were a good thing for Sm4sh, yes. But in a game with every veteran already in, your point about falls apart.
3. So then do you want Snake and Cloud cut? Metal Gear hasn't had a prominent release on Nintendo consoles since 2012, and at the time of his inclusion in Brawl he was advertising Metal Gear Solid 4, which didn't release on the Wii alongside every other Metal Gear game. Cloud, one of the largest 3rd party additions, advertises Final Fantasy 7, one of the biggest middle fingers to Nintendo ever regardless of Nintendo's association with the franchise. Snake represents Metal Gear Solid, a prolific gaming series (he was also a favor for a friend), and Cloud and Joker, while not known for Nintendo appearances, represent Final Fantasy and Shin Megami Tensei, two series with historical ties to Nintendo. The point here is that **** like the "console wars" don't matter, it's what the characters represent and their legacy that does.
Word from the man himself. You may not like it, but that doesn't mean it's unlikely, nor is it a bad choice.