How can I dynamically change a plugin's version depending on certain criteria?

buildscript {
  extra {
    "pluginVersionA" to "1.0"
    "pluginVersionB" to "2.0"
    "pluginVersion" to "1.0"
  }

  extra["pluginVersion"] = project.findProperty("buildingForB")?.let {
        if (it == "true") extra["pluginVersionB"] else extra["pluginVersionA"]
  } ?: extra["pluginVersionA"]

  gradle.taskGraph.whenReady {
    if (tasks.contains(task("buildPlatformB")))
      extra["pluginVersion"] = extra["pluginVersionB"];
  }

  repositories {
    mavenCentral()
  }
  dependencies {
    classpath("com.example:example-plugin:${extra["pluginVersion"]}")
  }
}

plugins {
  ...
}

apply(plugin = "org.example")