N707ZS, that option would indeed have been possible. Basically the same sort of MRTT conversion for the A330 which Elbeflugzeugwerke did for the A310. However, Airbus would far sooner sell a brand-new full-fat A330MRTT than sanction an 'A330MRTT-lite' conversion with no boom, 2 pods and a simpler Fuel Operator's Station including a Mission Computer System which actually works!
If the RCAF elects for a CF-188 replacement which needs boom refuelling, the current A330MRTT is the better solution. But if they restrict themselves to probe-and-drogue AAR, then an A330MRTT-lite makes better sense.
With so much underfloor space for cargo, the A330 does not need additional fuselage tanks or a KC-46A style extended centre tank. For passenger carrying, the seat can be left in situ rather than passengers having to use 'palletised' seatling in the windowless KC-46A with its 'rendition-class' seating.
Currently, the assumption is that the CC-150T will remain in RCAF service until at least 2028.