I know you said no cross-platform frameworks, but perhaps something to look at:
Write all the core logic in javascript. Unit test that at will. Then use tools like Appcelerator to turn that logic into native code.
Then import that logic code into your native platform projects for each of those platforms, and build out the other features you feel can't be achieved properly in any other way.
For platforms they don't support right now, you might be able to find a js to native code converter, or indeed a way of hosting a js environment within those platforms.
