Operating rafale one would expect, at the least, the tailoring to include catapults and angled deck, and the deletion of the ski-ramp. There is also the issue of the podded propulsors top speed and suitability for CTOL operations, is this being changed? A change from electric/podded to a more conventional power train would seem a major design change.
Altering the baseline to accomodate such items would de-risk any future decision of the UK to go CTOL instead of STOVL. It depends just how much commonality there will actually be and what they mean as the "basis" for their second carrier.