I don't think the cuts are a problem, really. The remaining surface area should be plenty to handle the forces and the groove will be a good grease deposit, I think.
Don has all my new polyurethane bushings. They'll be on their way here soon.
Are you using polyurethane lower control arm bushings or rubber LCA bushings? The reason being is the rubber has an inner steel sleeve pressed into the shafts.
If you are using polyurethane lowers i believe the polybushing will rotate on the shaft itself. Since this shaft has a cut in it, that will wear out the polyurethane bushing in short order as the arm rotates up and down.
If you are going this route with polyurethane lower bushings i suggest replacing that cut shaft, or at least filling the groove in it with JB weld epoxy paste, or some other metal based epoxy paste. I would not suggest welding on it. Because it may be hardened steel, and welding it could heat the metal to a point of removing the hardness in it.