I haven't read the whole thread (I can be lazy), so sorry if I'm repeating anything!
Being a Nintendo owner almost exclusively, I really have very little experience with DLC. Actually, I've only ever bought it once, and that was for Mario Kart 8. For about $15 I basically got a quarter of an entire Mario Kart game. Since I paid more than $60 for MK8, $15 for a quarter of a game is a great value. I've heard that typically DLC is overpriced, and offers things that should have been in the original release in the first place. If Playtonic wants to add on what is basically a mini-version of the entire game and charge accordingly like in MK8, I have no problem with it! Extras are always nice.
At the same time, the time and money spent making that little update could go towards making an entirely new, full game instead, so I'm a little torn.