arbor and guards could handle a 12″ blade it would be marketed as a 12″ saw. Mickey Mousing (sorry Disney)some adaptor to work will most likely end up producing a saw that will be dangerous to use and impossible to control. NOTHING in the drive train is designed to run a 12″ blade. Nor is a 12″ blade meant to run at the same speeds as a 10″ blade. It would be suicidal to try it.
I can’t think of any reason to mount a blade 2 inches larger than the saw is meant to handle. If you need a 12″ saw, then buy one.