RJs from KC-135s
Sorry Iwasaspotter,
That argument does not carry any water, except literally.
The impact of a career as a KC does not put any additional stress on a -135 airframe as service in any other of the many, many special missions the 135 fleet has performed.
Besides, the RCs did NOT come from EC-135s. Most of the current W fleet were modified from M-models which were originally converted from C-135Bs. Some additional aircraft were converted from Bs directly to Ws when the fleet increased (61-4125, 126, 130). The U and V models were purchased directly for the RC-135B role. Being in the last batch of KC-135As purchased, the three RAF aircraft are 19 years younger than the original KC-135A batch. Just ahead of the RC-135Bs, which were the last of the 135 production.
Since the airframes have all had the same wing re-skin, TCTOs and other general airframe work then the only additional modifications are the ones undertaken to convert them to the RC-W version.
There is no difference between the RAF conversions and the original existing RC-135Vs, except designation as a W. (Done recently for standardization as the original B models have electric flaps and the KC-135Rs, RC-135Vs have hydraulic.
Give it a rest! The modified aircraft are NOT different, except for the retention of water heaters for the required UK "brew-up" requirement.