Hey everyone, we just tackled this job here and found a way around the BMW socket. We took a 6 point 15mm and shaved down the outer walls. Worked like a charm with no issues on removal or installation.
Everything torqued and released just fine.
He are some pictures with a rough measurement on the dial calipers if you would like to be able to change these plugs without spending $$ on the BMW tool.
Thanks for all the great information in this thread.