I don't understand why the resistance to a courthouse wedding. The couple, the officiant, and maybe a witness are in a room together. The whole process takes only a few minutes....formal dress isn't even required for the ones I have seen....and the result is an official marriage certificate. That leaves no doubt for USCIS.
This is just the first hoop you have to jump through. There will be more immigration hoops to navigate over the next several years....one of which is increased USCIS fees beginning April 1st.