[GildorInglorion]

Interesting idea with the wights being lesser ringwraiths.
But I think the shadow Frodo could have turned into should have been very week and completely in the hands of Sauron. Frodo could not become something like a wight, they are powerful creatures, and I don't think they care much for Sauron.

If someone was stabbed by a Morgul-blade before Sauron regained his powers, maybe them could become like the wights the four hobbits met? And I'm almost sure that the whitch-king was a powerful force, perhaps able to make Morgul blades, long before Sauon started to regain strenght.

I also believe that men make much more terrible shadows, or wights, than hobbits. The strenght in a hobbit comes mostly from his / her good and uncorruptible heart, and it's exacly those things that a Morgul blade destroy.

And magic weapons seem to be really hard to produce. Otherwise I think Elrond could have given Boromir a better sword. Morgul knifes are also pretty useless in battles, what you need there is instant death (With-king chose a mace instead at Pelennor)