I think the problem with pellet is that they are made under a non-oxygen environment in long noodle-like manufacturing if I remember correctly. The non-oxygen is so you can keep them as unoxidized as possible during the blending/chopping up process, of course. They are blended up and then able to be packed closely together in a hard pellet. You could not squeeze whole hops in such a way without chopping them up. A pill-pelletizer could be come up with, but is it really worth it to oxidize your hops pre-pellet-making in the homemade realm? Myself, I can see whole hop plugs weighed and then squeezed together for "room saving only" in vacuum sealed bags. I just feel to make pellets properly would be out of most home brewers means, even with a device that makes a "pill" pellet possible.