1. I don't think you could make any sort of private servers for Spotpass, but I wouldn't know.
2 and 3. Both of the scenarios you listed mention 2 things that I'm pretty sure work quite differently, plus #2 seems very pointless.
4. Uhh... What?
5. Wasn't there that "amiiqo" thing that was similar to what you described? Also this may be possible but not very practical.
6. From what I've seen, 3DS emulation (On PC, if that's what you were asking about) is starting to happen, but it's in a very early stage.
7. This isn't going to happen because the SNES emulator that Nintendo uses for VC only works on the New 3DS.
9 and 10. There is freeShop, but I'm not sure if that works outside of CFW.
On #2 what I meant was just have Spotpass (as in people from your friend list) work as Streetpass, like you could use your 3DS friends in games like Puzzle Swap and stuff (IDK about having Streetpass as Spotpass).
On #3 what I meant was to be able to use online play as local play ((even though this isn't a 3DS game) i.e being able to play Nintendo Land online with other people).
And on #4 what I meant was to make Miis from Mii Maker enter your Streetpass Mii Plaza (without gold pants) and behave as if you had actually streetpassed them and you could be able to use them in games like Find Mii.