Engines, a well considered post, as always.
To increase flexibility & reduce cost/risk, why not leave the "other" refuelling system in place? Having watched an Air Force (RAAF) struggle with a seemingly minor mod to an off-the-shelf jet (they requested McD remove the catapult launch bar ("it isn't a naval jet!") leading to nose wheel shimmy on the Hornet) maybe less mucking around would be better? Didn't the F-105 have both systems fitted (random historical precedent for credibility)?