I have seen a Brabus enhanced bent-12 with four (two per side) OE inter-coolers with modified inlets and outlets.
There are several options for upgraded charge coolant pumps. We're trying a third flavor of pump in a friend's Brabus K-8. Aftermarket pumps have been failing faster then OE. There is nothing special about the charge cooling pump. 12 volt pump. Inlet and outlet needs be in desired orientation. We want increased water flow without excessive current draw. The previous owner of the K-8 installed (poorly) a relay to power the charge cooling pump.

OP what are your power goals? Have you measured charge temperature, pressure drop across the charge cooler core and the like? I'm curious as am preparing to find my way down the same rabbit hole with my S-65.