Challenges Google must face to employ Swift in Android development:
1. Swift was developed as a replacement for C# so technically google can't directly use it in it's source code, rather some changes need to be brought in the source code.
2. Specifically, Android would need a runtime for Swift.
3. Google would also have to make its entire standard library Swift-ready, and support the language in APIs and SDKs.
4. Swift would also not be useful in bridging higher level APIs in Java; they’d have to be re-written as well.
If we were talking about Go, which was created by Google, I could take it. But language made by Apple for iOS, nah.
In order to write apps in those languages you listed, you need Android Native Development Kit (NDK), and here is a quote from Google about it: