Hmm... Some of the things that you - the OP - listed are not typically released as DLC. When they are, many fans see them as a sort of means to "fix" the game rather than add an [enjoyable] quality to the game. However, the fact that fans find Skyward Sword lacking in various areas seems to suggest that [some] fans wouldn't mind a "fix."
I think it's worthy to note that SS is a linear, story-heavy title, and as such, its dungeon progression moves the story along. That said, it might not be in the best interest of Nintendo to add DLC to the game, unless it doesn't interfere or tamper with the plot in anyway. Thus, DLC would likely be limited to more enemies, a few upgrades, and aesthetic changes to Link (and other characters). Any dungeons released as DLC would likely be minigame-esque in design, as to avoid tampering with the game's plot.
DLC [in SS] seems like a terrible idea, if you ask me.