I would love to see this as well. The CLR is a better VM and the ecosystem on the CLR is richer now than it is on the Java side IMO.
Kotlin code would not be write once run on either JVM or CLR though, at least not trivially. Kotlin data structures have java data structure semantics, which in turn are different in the CLR. They could be wrapped with a thicker layer to hide the difference though.
I would be happy to devote time to help such a project along.