My bad! I’m so knife-centric I was unclear. In this case, I’m talking about a tool to remove wood from a handle to make a slot for a tang. A different one may be needed for each tang thickness, but you are talking about the more common use of the word. Except I forge smaller items (if I can claim a specialty, it is smallish wood carving blades, though puukkos are a strong interest, as well), so I was just thinking of trying to make a task I find annoying just a bit easier. You work larger than I do, as well. Your tooling will reflect that, so this was probably a poor suggestion.
In that case, something that has interested me since I first started even thinking about smithing is the concept of portable tooling. Whether something like the Madtermyr find or more recent, such as Wayne Goddard outlines in one of his books. If you were to set up a five gallon bucket with all the tools you would use to be the modern version of a journeyman (carrying your tools with you, setting up wherever you can put the anvil, etc), what would your setup look like? What assumptions would you make about any potential work sites?
Of course, this may be of interest to nobody but me, so take it only as a thought.
Patrick