Like where this is going.

Couple of constructive suggestions re the back story (bear in mind I can feck off as well as anyone though....

)
1. Perhaps the "fighter mafia" in the USAF successfully resisted the move to make the F-16 heavier and multi-role, so in this 1983 they're still all lightweight, sparsely equipped A/B models. The USAF then buys into the Eurofighter as an alternative way to get a medium-weight "swing fighter". Alternatively, instead of buying into the Eurofighter, why not have them buy into Tornado instead of developing the F-15E?
2. Perhaps the "GR" designation was political, being adopted instead of "B" to avoid giving the impression that the RAF was back in the strategic (i.e. nuclear) business and thereby putting the RN's nose out of joint and alarming the Soviets. The ".3" could be because two extra 2nd hand airframes were delivered first in order to start training, with one of them having no RAF mods and the other only partial RAF mods. Thus they became the only examples of the "Lancer T.1" and "Lancer T.2" since they are only used for currency training to spread the airframe hours out, not for operational missions.