I don’t like the the figuring that goes with it. Seems the offset is not always the same. When I make a template I find it much easier and more accurate to cut it exactly to the size and use a bearing bit. I know there are cases you can’t do that, but not many. Particularly mortises I can’t see a guide bushing there at all.Please be specific why you don't like bushings, you are a far more accomplished woodworker than I am, would like to hear your experience with them. For me they've been great, often for things like oval cat holes that don't need precision, but also stuff like dovetails and experiments with inlays.
Re bearing bits, the cutting diameter limits how tight a corner you can make. After routing you hand chisel the corners?