Can't use dropdown form fields as display fields

Can't use dropdown form fields as display fields

Hi,

I have a SERVICE subform that has a SITE look up field. I want the SITE lookup to display the site name and site address.
However, when I go to Edit Field ->Advanced Options -> Display As, I do not see all the SITE fields. The ones that are missing are the dropdown fields so I cannot select site address. Note, site address is a dropdown in the SITE form.

Is there a way that I can use the site address field as a display field in the SERVICE form without making the site address a textfield in the SITE form?

What is the best way to overcome this issue?