(Wannabee knifemaker and machinist in practice, but know some theory)
That pulley wheel gives me an idea:
That pulley wheel Limits what you can do with the sanding belt while the disc while is attached.
Monster grinding contact wheels are becoming more popular right?
Why not combine the two concepts?
Have a ten inch or whatever size wheel with the standard rubber tire mounted on a rim that extends back towards the hub while parallel to the axis. On the empty side of the wheel, attach the disk. A drum contact wheel of sorts.
Construction:
If I am guessing right how that wheel was made (in two pieces), here are the extra steps: Braze or weld, using extra thick fillets and beads, two semicirlular strips the width of the grinding belt to the rim of the disk. (two joins instead of one in order to keep it balanced) Reassemble to hub and use lathe to remove excess filet/bead inside rim. Retool lathe and bevel disk if needed. Retool lathe and turn the wide brim circumfrence to the final diameter which fits standard contact tire.
If centered properly while on lathe and the joins were diametrically opposite to begin with, it will be balanced when finished.