Because Reason is just a syntax layer over the OCaml syntax, you should write an MirageOS unikernel with Reason. However, because MirageOS needs lot of works, lot of people of this community don't have a plan to switch to Reason - but feel free :) !

After, it's about a convenience easy way to compile your Reason code with an OCaml code. Reason is just a preprocessing, you should use the `-pp` option with /your favorite build system in OCaml/ and, I think, it's enough.