Just reading this what comes to mind is increase in inertia mass (6" vs 4.5" dia), this most likely lesser of an issue for the motor than the friction vs torque output.
Most Machines (Especially Craftsman) misrepresent the true power output of the motor, thank marketing for this. This marketing deception is rampant EVERYWHERE. Us buyers need to be informed or we get duped. The other place we see huge deception is in Lumen ratings in light bulbs......
FYI 746 watts= 1 hp roughly 7 amps to 1 hp. Keep in mind all motors run between 85-90% efficiency so, in order to get a true one hp it needs to be 1.1 hp or 8amps/120 volt rated motor.......... All this is lab calculations not real life but it gets you some starting points to work with.
That said, if the motor power is ample to resist the increased friction, then it would work ok. Bear in mind the old 4.5" dia has a roughly 14" surface area and the 6" will be about 19" surface area.
Without getting into a bunch of math, this is what will increase the work burden on the motor. Surface area. The increased inertia from this will be the lesser impact on the motor except for the startup impact.
My own real life experiences have showed me if the motor is a true 1hp motor, it would work ok (assuming it is a 1to1 direct spindle) above that, you will be able to hog in on the work if that is the need, below that, you will be going slow and lighter push based on the slowing sound of the motor, and will shorten the life of the motor. Damn, I planned on writing just a couple of sentences.....