I don't recall the following being challenged:
https://xoutpost.com/bmw-sav-forums/...s-summary.html. Phil is our resident expert on transmissions, might want to PM him for input.
Transmissions and engines are designed to run most efficiently at a specific operating temperature. The same is true of the life of components.
Lots of my laymen solutions sounded very logical but I have learned over many decades to find verification from the MFG or aftermarket performance suppliers. When there is a design weakness or flaw there are often MFG revision part numbers. When there is a chronic weakness that the MFG has not addressed there are often aftermarket solutions well recognized as a design improvements.
It's true that engine temperature is specified to help meet emission standards. That doesn't mean it shortens the lifecycles of components or that by reducing the temp the life can be extended beyond the design specs.
I'm not saying either of you are wrong, or trying to change your mind. I can see you are convinced you are right. I am saying you have no expert verification for what you are doing. You don't know you are right.
I been where you are many many times over the years especially early on. Usually I was doing what seemed to be logical to save money, in denial. My advice is to close that gap between what you think you know and what you don't know as part of your decision. For what it's worth I've learned it is far better to do the right thing the first time. Lots less pain, suffering and cost over the long run. Good luck