The RAFAT task is as much political for the nation as it is for the RAF. If the nation wishes to have a rapidly deployable, flexible tool for international influence, as well as advertising the current capability of British industry, to the hopeful benefit of the nation, then having them operating a Hawk which represents the current capability of both the platform and British industry would make sense: RAFAT could be using the latest mark of Hawk, with slats and T2-like cockpit and mission computer.
This could increase the performance of the aircraft for air shows, and show potential customers what they could be buying today or tomorrow, not how great a platform was available from 1976 onwards amongst rather different competition of the day.
That there is sufficient FI in the fleet to get the T1 to 2030 isn't really the issue: the ever-recurring question of replacement has merely been kicked further down the road. Other nations with very junior aerospace sectors are pushing hard to develop them, but the UK does not appear to have the political will to push such a strategic industrial capability.