That was the idea I had many moons ago when I first realized my Square Wheel was way too fast. It comes from the factory, with a cast 10" drive wheel that moves the belt at 4600 SFPM, and is the major problem with the machine being a "knifemaking" machine.
The factory drive wheel cannot be reduced in size because of it's factory configuration (there is only a "web" of material connecting the outer hub and the arbor hub), therefore you're left with the option of either obtaining a "slow down" wheel from somewhere....and for a while that was an option, but as the Square Wheel sorta "died" away, those who offered the slow down wheels ceased to offer them.
About the only choice a person has these days is to find an 8" dia (or larger) X 2" thick chunk of aluminum (can't use steel, the weight tears up the motor's braking system, and destroys the motor), and have a drive wheel machined out. The smallest drive wheel that can be used without modifying the tooling arm's position, is 8 1/4".
You can go down to a 7 1/4", but that requires re-positioning the tooling arm as far outward as possible....meaning you have to drill/tap new holes into the grinder's frame. (This is what I did to my Square Wheel).
A 7 1/4" drive wheel slows the belt down to approx. 2800 SFPM. It's not ideal, but it makes the machine a far cry better then the factory 4600 SFPM.
At the time there was no such thing as a commercially available VFD.... In the current time, a 2hp/3ph motor and the associated KBAC VFD is about the same cost as having a new drive wheel machined out...... considering that the costs are approx. the same, there's no question that I would go with a VFD setup if I had it to do over today.