Android :: Way To Get Extensible Apps With Scripting / Bytecode Downloading?

I'm looking into a solution that needs apps to be dynamically extensible. One way could be an extension language or scripting engine. I've seen the Android Scripting Environment, but this needs the actual C scripting engine (Python or Lua) running as a separate process. I would like the runtime to be a Java app itself, like JavaScript using Rhino (and not using a WebView). Another way is to download Java code dynamically. But, Android does not support jar downloading and dynamic classloading, since these bytecode class files are not used directly.