I don't recall hearing about an OE trans cooler failing often enough to really be a concern for the normal daily driver folks...
You can convert to a generic oil cooler configuration for more efficiency. This works really well if matched with a 1m rep bumper and 1m ducting, with one side for the stock oil cooler and the uprated trans cooler on the drivers side.
Here's a random example, but there are lots out there:
https://burgertuning.com/products/n5...mission-cooler
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1and1
135i - E82.N54 2009 BSM - MHD / xHP / DCI, PR CP & 7.5" Race IC / N55 mid & Borla
. . WL RSFI, Koni, Eibach & Dinan CP's, M3 CA's / EBC Red's & Firehawk 500's
X1 - E84.N20 2013 MGM - JB4 - The Wife's, now with new turbo & ewg