Unfortunately it's impossible to combine that with seamless Java interoperability, because so many Java features are dangerous (null, exceptions, pervasive mutability, all of the methods on Object, finalizers, low-level thread manipulation) or at least cumbersome (use-site variance and the resulting existential types, control flow constructs built into the language syntax).

I don't think there are any dangerous things you can do in Scala that you can't do in Kotlin. Only safe alternatives that exist in Scala but not in Kotlin.