The problem with having an "Android emulation layer" is that it won't be an emulation layer, because Android was meant to be used as a complete OS.
Android isn't like SDL; you don't choose to use it because it's got some cool features and fast blitting, no, Android is like a meta-operating system. It uses its own power management API, its own security API, its own data storage API (When an application is uninstalled, *all* of its data will be removed, and its guaranteed to remove *everything* because an application is never allowed to write outside of its own data directory) etc.
So if you run Android like an emulator, the situation will be weird, because in Linux you're used to e.g. using "mount /dev/... foo" to mount an SD card, while Android has its own APIs for mounting SD cards, so there will be conflicts (In Linux you have to be root to mount an SD card, so Android, which runs as non-root, can't unmount SD cards mounted by raw Linux).
Now, I'm of the conviction that the Android system is more stable and less fragile compared to the raw Linux system (e.g. in Linux, you can cause damage by pulling out an SD card while it's mounted. Or Linux may lock an SD card so you can't unmount it. Not so in Android) so that's why I'd prefer that system. But I realize that I've got a dev's POV and can't expect all end users to think like I do
PS. It's 04:52 AM here right now, so I'm just spewing words right now to get what I want to say out there before I fall asleep