If DLC is used fir Smash Bros at all, I guarantee you it will NOT only be used for minor things such as music. While it would be nice for Nintendo to consider the fans when creating their product, we need to remember that at the end of the day, its a part of business.
Nintendo has to know that DLC Characters are what will make them the most money, as very few people would likely pass up a new character for the game. To simply release minor things that could have been in initially just doesnt make sense, even if they were free. If DLC is used, i'm positive it would be used to the farthest extent possible, and that would be characters and stages.
Not to say music wouldn't be included with the characters and stages, but to think that they would only release such things and not give out the cash cow, I highly doubt that.
Frankly, if you don't want to have to buy DLC characters, or don't think they should be included, remember that it is OPTIONAL to purchase DLC. So if you don't want it, you don't have to have it.
This isn't at anyone in particular, but I just remember there being quite a few people arguing that, and it just wouldn't make logical sense.