I think you'd look great in a Lanai, Ingunn. I found the Lanai pretty TTS for me. I have a 2. (If I keep it -- that is still to be determined!) I could possibly wear a 0 except it might be snug in the shoulders.
This jacket is more forgiving than some because it is an open blazer. The main issue for fit with this is not being able to "fill it out." This is my problem with it, but would not be yours, I suspect. It's a function of my long neck, smallish frame with wide shoulders (sounds like a contradiction but isn't, really -- in Claire's terms I am "elliptical") combined with my small bust.
This cutaway style jacket is pretty much a slam dunk for those with a shorter neck, fuller bust, and/ or apple shape.
I think your body type will determine whether or not you consider Theory TTS. Generally they cut for a smaller frame and somewhat rectangular shape, I believe. But the Lanai is a jacket that seems to work on a lot of different bodies.