With the Belleville washers, think about this, the tapered roller bearing, when side loaded, as when cutting, would naturally try to deflect, and climb a bit out of the outer race, this force will be countered by the rear bearing, but the spring washer will have to allow some movement in an axial direction, and that compression of the washers, however slight, will show up in the finish of the workpiece. If the compressive preload force of the washers was to exceed the axial forces of cutting action, then there may not be a problem. But it would be a fair amount of work to find out.
To groove the bearing cup EDM would be first choice, but at a $$$cost. buy a carbide grooving tool that is about half or a little more that the groove needed, about 250 sfm and plenty of lube, may need earphones for the squeal.