the cooler is not under much pressure internally, the radiator is under 20 psi when the coolant gauge is at 90C.

I assume that the construction of the cooler makes it such. BUT there are hordes of W211 owners who have faced coolant in the transmission - The toyota and nissan truck owners also have faced $4000 bills to replace their watered transmission from cooler failure.

Those guys stick a big air ATF cooler upfront and call it a day. Im thinking of this too but get confused on the heat exchange capability of it compared to the original intank cooler (which is plate type too and water has at least 10 times the cooling potential of air)

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)