Start with the Vietnam hawk design, but instead of the convex underside, beard it. Keep it sharpened, if you're really ambitious serrate it so it would bite on hooking moves, don't know if this would be best though- a hook turns into a trap if you can't get the thing off somebody's sleeve. Thought a triangular or diamond cross-section back spike would be good, but starting to like the tanto idea; just wonder whether the point should be high or low. If it's high (toward the eye) I'd be a little afraid the "belly" would hit first and glance off. Maybe one of the Wharncliffe-Tanto hybrids like the RTK, with the point at the lower edge and a little curve. Would give the spike hook & cut potential.
As to steel not sure you could reason from experience with knives (where most of mine is). D2 seems a good choice.
Seems like a metal handle might rattle your wrist on a hard hit, also would worry about brittleness with such a long handle. Somebody who knows more about metal might correct me on that. Fibre-reinforced synthetics seem like a good choice, maybe with embedded langetes.
Also like the idea of a flat, easy-to-carry hawk with mostly steel shaft, but wonder about how you'd zone-harden it. (not an expert here, just thinkin')
For all of them I'd make the cutting blades thin for deep clean cuts in soft material and the head relatively light with a medium sized handle that doesn't get in the way if you need to choke up. Option for a long (ie two-hander) handle.
