Re: If you buy it do you own it? ...or... Will the device start overlaying Ads over the photos?
Here maps (from Nokia) works well for offline maps on Android. I haven't looked to see if the maps can be synced with rsync though. Maybe, if you're rooted. Obviously Firefox and VLC are already available. If you don't log in to a Google account for anything, you can be quite Google free if that's your thing. It's convenient to have an app store of some kind though. Perhaps install Amazon?
A lot of phones have dual booting options available as well, if you look on sites such as XDA-Developers. Invalidates the warranty, I'd expect (some people disagree about this saying EU law allows it).
I think hypervisors will become popular in time, particularly as Android phones are now starting to ship with 3GB of memory.