N-Reg option has been discussed at length, with regards to airworthiness limitations. Depending on which FSDO you speak to.
The Austrian option, well you will need to speak to him, I believe he has an approval from the Austrian Authority to run past the 12 year mark for the airframe, but still adhering to the 12 year life of the blades. Has a fairly indepth annual inspection, frames inspected etc.