One of my players have set about to create a Wizard's Leap style spell.
He's specifically mentioned he's planning to use it to teleport into/out of a faerie regio theat they are having ...problems with.
Would this work?
I always thought that you couldn't cross Regio borders like that - if you walk towards the edge but fail to cross the border, you find yourself headed back towards the center.
Depends on the regio, I believe. Some regiones can be entered simply by crossing into the borders when aware of them (and sometimes when not), whilst others require specific circumstances and behaviour to enter. I'd allow teleportation into the first class, but not the second, unless you could somehow fulfil the conditions whilst teleporting.
I'd go with that. And have. Regiones are supposed to be a little bit variable (or they are in my book) so as long as you don't play too fast and loose with the concept you can pretty much get away with anything. But bear in mind, that the majority of regiones should work exactly like the troupe expects (rulebooks be damned, it's the troupe that counts). So develop a baseline and deviate only when the story demands (or looks up pleadingly, tears in its bright blinking eyes) it.
I tend to not allow teleportation across regio boundaries, but could well make exceptions for some regio's
I allow teleporting across regio borders but at a massively raised spell level.
I would never allow it at anywhere near normal Tp spell levels.
How massively?
What if the magus is already using Leap of the Homecomming but only want's to move 2 feet - as long as it's out of (this level of) a regio?
Mmm, if accounting for us running with higher base levels for teleporting overall i think its +4 magnitudes for into/out of a Regio. And + the Regio level(s)(ie. if between different regiones add the levels of both, but if between levels of same regio only add the difference) upon that.
Mmm might be 2+regio level adjustment though, its a long time since this was used so my memory isnt exactly spotless perfection itself... 
And i would say, 2 feet, 2 million feet or to the other side of the universe, its still out from a regio which means adding a major level of "tricky" to it regardless of actual distance.
One saga I played in we ruled that teleporting into and out of a regio required
two magnitudes per level of difference, so teleporting into a level 2 regio would
require four extra magnitudes.
We also ruled that teleporting somewhere applied the aura-modifier and extra
botch-dice from the place teleported to.
According to the book the important thing about crossing into Regiones is the ability to sense across the border. Once you can see where your going you can "walk" to the next level. Though in practice you should be able to run, fly or take a boat to. Since hermetic teleportation also requires you to see where your going (unless you have an arcane connection) it shouldn’t be different from any other means of locomotion.
Where it gets iffy is trying to use an arcane connection to teleport without sensing across the boundary. Personally I think the sympathetic magic inherent in arcane connections should let you cross regio borders freely as well. While it’s not exactly the same thing, I’ve never heard anything about spells with range: arcane connection not being able to effect things in regiones. (like the idea of applying the aura modifiers at that target sight as though)
What about simply requiring Penetration to teleport across regio boundaries? Assign each level of difference level 5 'Resistance'.