What requirement does Apple put on the JDK location? All of mine are in ~/lib/* and are easy to manage. JENV for bonus points. Definitely not a double-click-install experience, but not hard to figure out for anyone with a bit of terminal experience.
If you want it to be recognized by the system as a valid runtime for Java apps, I believe it needs to be in /Library/Java/JavaVirtualMachines/jdk${VERSION}.jdk/Contents/Home/.
