My thoughts:
Option 1: One benefit you haven't mentioned is that this would enable you to charge your phone at the same time, ensuring you're never left without power. Now, granted that means you getting your phone out of your pocket to do so, but using it as a navigation device. If you have it mounted at the correct level, then you wouldn't need spoken directions (indeed, I find them irritating so always turn them off!). Data streaming maps would be a no-go, however you'd simply buy TomTom for iOS and use that instead for £35. I have the UK, Europe and US versions, and they're all superb. Pop a new head unit in and you've got your streaming as well, as you say. This has the added benefit that you always have your satnav with you, regardless of vehicle.
Option 2: I don't see a massive benefit here over the above option. Sure, it will be a bigger screen, but it will also be further away than the iPhone so maybe negligible difference? That's where I had mine mounted when I had a Zed, and although it worked well it's not something I would use these days as satnav on phones is a much more realistic and usable proposition.
Option 3: I personally wouldn't touch App Radio with a bargepole until a couple of generations down the line.