if your using CIA versions of the games then yes noone so far has been banned from using CIA files i think
That should bw fine. I actually play online with out of region cias a lot and I haven't been banned. The only way I see a ban happening is if you use a ROM hack (even this I'm not sure of) or cheats online.
it's safe
You can use Phbank (a homebrew version of Pokebank) but that probably won't work with Sun and Moon when they come out.