Generate a RANDOM application id and package name with Gradle Android build

I'd like to make Gradle substitute the applicationId and package variables with a random string at build time. Here is was I tried:

// build.gradle (project)
class Scrambler {
    Random random = new Random()

    String getRandomString(int i) {
        return random.with {(1..(6 + random.nextInt(i))).collect {(('a'..'z')).join()[ nextInt((('a'..'z')).join().length())]}.join()}
    }
}

Scrambler scrambler = new Scrambler()

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.${scrambler.getRandomString(2)}.${scrambler.getRandomString(2)}"
        // com.ohukcgn.vpybhkh (example)
        ...

At this point, all java classes are still bind to the original package name:

com.ohukcgn.vpybhkh/com.original.name.MainActivity // example

And that's legit because I did not change the path for them.

But now, what should I do to have a complete refactoring?

com.ohukcgn.vpybhkh/com.ohukcgn.vpybhkh.MainActivity // goal

I could do a script for that (that would rename directories and so on...), but I'm not sure would be the right thing to do.