An Example of a crude rocker guide that might work, but needs a re-design by someone who has better mechanical intuition than me:
You have already figured out how to trace the edge of a blade onto a piece of paper, to record the rocker profile. Great!
Now do the same thing using an Xacto (or other brand small thin) knife on a flat piece of stiff cardboard, to create a thin guide piece. This will be your "guide". Tape or clamp this piece underneath the blade or blade holder, 1/10" or so back from the edge, parallel to the edge. To verify that it is parallel, use a measuring tool, like a calipers, micrometer, or maybe just an adjustable divider, or nut on a bolt, to verify that the distance to the edge boundary is the same at both ends.
Tape or attach a "stop" on the flat surface on which the blade holder slides, next to the grinding wheel, but 1/10" back. It can even just be a piece of thick tape, stuck onto the surface. The thickness should be chosen so that the piece of cardboard, or whatever, touches it and is stopped by it, and never touches the grinding wheel, but the blade holder or blade passes over it.
Thus you can slide the blade or blade holder on the table against the stop. It will follow the established profile, and allow the wheel to grind the blade in the same rocker profile it already had.
Actually, you should reverse the order of attaching the guide and stop. Attach the stop first, and leave it there, then position and attach the guide, using the measuring instrument, to make sure you will only remove .001" (or whatever amount you want to remove) of metal.
Can you figure out a way to make that more practical? I admit that cardboard would wear out too quickly to last very long. Are there soft plastics, real or artificial leather, or some other material, that would retain their form, yet be easy enough to cut precisely?
Also, is there a practical way to cut it with a modified shape, if you wanted to modify the rocker profile? E.g., could you grind the edge of the guide, instead of the blade, to the shape you want, until you have it just what you want? I'm fairly certain that cardboard wouldn't hold up to that without distorting, but maybe one of those soft plastics or other materials would.
Another plausible way to create a modified profile: There are "Cricut" brand automated fabric cutters, which follow a computerized pattern, available in fabric shops.
https://cricut.comThe idea is to have it cut the guide, instead of using a hand-guided knife. I've never used one. I'm not sure if you can create your own pattern for Cricut machines, and whether the pattern can be curved. I'm also not sure if they can cut a thick enough piece of reasonably stiff material (e.g., real or artificial leather) to guide your blade against the stop. But if they can, that would be a very neat way to do it.
If you are really ambitious, let's try to modify the toe pick: When you cut the guide, cut against the toe pick shape too, so the guide includes the toe pick profile. Tape or attach another stop on the table-like flat surface on your bench grinder. Use that and the guide to cut the toe pick. I can't figure out how this could work with cross-cut toe picks, but many blades don't have them.
However, there are problems with re-grinding toe picks: the existing teeth (picks) are at an angle, which means that when you grind off the material, you are left with thinner teeth, because part of where the new teeth would be has already been cut away. If you care, you might need to modify the toe pick shape in some way.
Anyway, I leave it to you guys with real mechanical intuition, to figure out a better way to do these things. I admit it is very crude, and I'm sure you can think of something better.