Since no one else has answered your post I thought that I would. Depending on the skimmer that you have yes it is possible to do what you want to do. Of course anything is possible. With that said would I do what you want to do. That would be a big NO. I have a client that when the pond was built had the same problem except the skimmer was cemented in and the contractor who built the pond did what you wanted to do to raise the water level. Needless to say this pond started to leak after about two years. She asked me to find the leak and fix it. We determined that it was leaking where the face plate was raised. She didn't want to replace the skimmer so we had to fix the problem. Yes we did repair the problem about seven years ago and it is was fine until she decided she wanted a new skimmer this year. The repair cost her more then half what replacing the skimmer would have cost her.

Tell your husband that digging out the hard clay is far easier then trying to do what he wants to do. The next question is there any extra liner under the opening on the skimmer? This will determine how easy or hard it is. How far do you want to raise the water level? What brand and model skimmer do you have?
Mike