On the "out of character" debate, I'm going to say that I agree, it was surprising to hear Momo of all people plotting doom and destruction. But I'm not sure we can entirely credit to Momo changing - it might be our perception of what she says as the reader changing because she does look different. Things that Momo has said in the past, back in the "aww, tiny Momo" days may have looked entirely different coming from her new chassis.
As far as the job goes, we can't forget the coffee shop run entirely by AnthroPCs. I don't think it's very likely for Momo to end up working there - for one, Marten wrote it off quickly and it seemed to be more of a gag than anything else, and for another I think Momo is going to end up working somewhere we've already seen.
I'm thinking she might end up working at the chassis store, if only out of my own hopes to see Charlotte again.