Has Microsoft, Nokia, etc considered some kind of app api bridge or outright code converter tool for Android/Java apps into their own native SDKs?

Seems that if a lack of apps is your main problem then easing the time to port an app to your ecosystem should be a high priority. Sure you'd have to re-implement some proprietary api features, but they likely already have equivalents in the Windows phone SDK (location services, in-app purchasing, etc).