delighted with <> delighted at

Yeah, you can certainly be “delighted with” something. Just not “your position with us.” It doesn’t quite add up, because the “position” in itself doesn’t seem like it should be inspiring the delight.

Here are some more natural examples that I came up with:

I’m really delighted with how much progress the students are making.
The director was delighted with the glowing critical reception for his most recent film.

I think, as in the case of “enamored,” there isn’t really a strong case to be made about which preposition to use with “delighted.” OED gives “with” and “at” as equally valid (historically, “in” was possible but not any more); my instincts say that “by” would work too.

The key thing is that you want to name the proper “delightful” element.