Good observation. I believe you would use

  withFADR :: (FragileAndDangerousResource #-> Unrestricted a) -> Unrestricted a

One can't tag "linear" values in the type system but one can tag non-linear "unrestricted" values. See "borrow" in Section 7.2, page 5:26 of https://arxiv.org/pdf/1710.09756.pdf