I didn't quite understand this: "a sith could not a light jedi." Do you mean that a sith couldn't defeat a predator or a jedi? I don't like the jedi more than either Fett or the predators, it's just that a powerful enough jedi, such as Kenobi or Skywalker, is the perfect fighter without needing anything more than one (specific) weapon. I mean this without any personal bias. Keep in mind that I'm not intending this claim to include all jedi, but only the ones focused on combat, (the Guardians), or the most accomplished of the other types. Can you see any predator defeating Yoda, Mace Windu, or Darth Sidious?
Your point about the difficulty of defending against something other than a lightsaber blade is interesting, and I've given this a lot of consideration already. My theory on how alternate attacks, such as kicks or strikes to the weapon's handle, penetrate a jedi's defenses is that it is a non-vital action taken when a jedi's focus is on the vital threat of the lightsaber's blade. When blasters are fired, a jedi defends against those because they are the most threatening, but it would be child's play to do the same against something physical such as an arrow, bullet, or any other physical profectile. (Luke should have parried Fett's lanyard cable in ROTJ, but it looked cool that he cut it after it wrapped him.) If the predator's Smart Disc were used against a jedi, it might get chopped in half, but I'd doubt it would hit. This opens up the question of which of the predator's weapons, if not all of them, are able to withstand a lightsaber. In KOTOR, there are metallic swords with a "kordova (sp?) weave" that can repel an energy blade, and they aren't always vibroblades. I believe that vibroblades are always made of this metal. It would be a safe assumption that the seemingly indestructable material of the predator's weaponry ("that doesn't show up on our periodic table") would have the same ability.
I don't think a strong jedi would have much trouble with anything in the predator's or Fett's arsenal except perhaps the area effect weapons that stun or blast (grenades or bombs). It would be one hell of a fight, to be sure.
Getting back to Boba, I'd like to consider which of his weapons would be effective on a Yautja. I think we can rule out the lanyard due its strength and the speed which it could slice the line with a wristblade. What about the flamethrower, blaster carbine, and rocket darts?
"Be Like Boba." J. R. Duart -2006
WWJD - What Would Jango Do?