There are unikernel implementations in a number of other languages [1] but one of the benefits of OCaml has turned out to be the module system. I don't know much about Rust but I don't see any reason this couldn't be attempted. All the Mirage libraries are open-source [2], so taking what we've learned from these might be useful.

[1] http://deliveryimages.acm.org/10.1145/2570000/2566628/madhav... (taken from http://queue.acm.org/detail.cfm?id=2566628)

[2] http://github.com/mirage/