Well I finally found some all-season tires in 225/45R16, and it looks like they are literally the only ones available in this size. They are the Maxxis MA-V1, and i found them on onlinetires.com after reading about a user's negative experience with them on an E30 BMW forum. Apparently E30 M3s are picky about tires though. There doesn't seems to be a lot of information on them out there. Apparently the company is a Taiwanese mountain bike tire manufacturer that recently branched into automotive tires. Their bike tires are well-reviewed, and some online reviews of their car tires were generally positive, with a few complaining about treadwear.
TL;DR Does anybody have any experience with the Maxxis MA-V1 all-season UHP tire?