I had something similar to repair a few year back. What I did was to get a stainless steel 316 grade adapter plate made. This was in effect a ring that the skimmer bolted through in the normal way being larger than the skimmer it was then bolted through the steel wall of the pool. Plenty of zinc rich paint used on the old steel and a polymer sealant not silicon used where required.

Have to see if i still have a picture or not.