In the same way we have overlapping/incoherent instance pragmas which can be applied on a per instance basis, it would be good to have a -fno-warn-orphan-instance pragma which can be applied on a per-instance basis.

Annoyingly, there is not an obvious syntax to use for this case, since SOP for a module with orphan instances is {-# GHC_OPTIONS -fno-warn-orphans #-}