Re the tool mounting angle required, as shown in post #6, I'm thinking the reason no one has done it before is that the relief angle under the tip would be so much that it would be too fragile.
There's the criticism I've been looking for.
It's quite a bit, yes.
Another option is to grind an entire blank into more of a diamond. The tool would then be held more vertically; it wouldn't have to be leaned over as much to achieve the 60 degree inclusion angle.
This would be a bit more up-front work, but regular grinding will be just like any other tangential tool.