It's the internet so it's impossible to tell how much of this thread is meant as a joke vs serious, but regardless I'll add my genuine theory here instead of creating a new thread.

In my interpretation, the camera gives way too much time and cinematographic love to the Nutkin in this trailer for it to just be there for funsies. Because of that, I think it's (plausibly deniable) planting that sets up for a payoff that will be revealed in the final trailer.

Here are several hypotheses as to what that reveal might be:
- Among Green Mage's arsenal is the ability to turn into animals, and the Nutkin is Krile.
- Green Mage has animal helpers, and the Nutkin is Krile's helper.
- The new limited job is Beastermaster, which has animal helpers, and the Nutkin is one of them in the trailer.
- The new limited job is Puppetmaster, which has minion helpers, and the Nutkin is one of them in the trailer.

It's always possible that the Nutkin is just there for fluff, but I don't think it's likely. Regardless, we'll see soon enough!