I think it would be the other way around....RAF are scared if they went down that route, or remove focus from the B, that the RN could make the logical case that F-35B, with its associated budget, should be assigned totally to them....particularly as the likely total buy of 74, opposed to the still touted (but utterly untrue) 138 means that Carrier Strike and a limited land based Expeditionary Capability inevitably becomes the main focus of the fleet....one of which is definitely the RN's area, and the other could reasonably be as well alongside the RM, ship based long ranged fires etc...and with the RAF's investment in heavyweight AAR in the form of Voyager, future unmanned capabilities and GCAP's emphasis on extreme range (allied with increased range air launched stand off munitions on the way) its a fairly reasonable position....as the RAF appears to be pivoting to a force that (sensibly) will launch from increasing distances from the enemy on main bases.