Now it seems that a few of the Forester guys are running 215/70/16's without any real dramas. Is there any reason that I couldnt get away with this size on the Liberty? I wouldn't mind this size it'll give a little extra height and a few more AT tyre choices.
The other option would be the Yokohama AT/S in 215/65/16 or the Bridgestone D693 in the same size.
Last concern - the legal implications. Jumping from the standard 195/60/15 to 215/70/16 is a pretty big leap. I guess it's another reason to start with an Outback in the first place.

Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/km Difference
195/60-15 117mm 308mm 615mm 1932mm 518 0.0%
215/60-16 129mm 332mm 664mm 2087mm 479 8.0%
215/70-16 150mm 354mm 707mm 2222mm 450 15.0%
215/65-16 140mm 343mm 686mm 2155mm 464 11.5%