IIRC the only tankers which isolated the tanks for the receiver in order to carry a separate type was the KC-135Q/T (for the SR-71).
The down side for the conversion is that the receiver fuel now becomes pure cargo, limiting tanker range/offload flexibility, giving requirements to be able to have separate fuel dump and measuring systems etc.
I am sure it could be done if necessary - and the KC-45s greater capacity would allow the carriage of a greater combined total, retaining as much as possible of the original performance figures.