I agree with getting the rocket turtle, and also I would like to see what fighting the tweedle boss would be like. He sounds interesting.

But new bosses, eh? Hmmm...

There's one thing I'd like to see in JJ2.

All the current bosses are the same size as Jazz (pretty much, a little bigger or a little smaller is it.) And I'd like to actually see a boss that's bigger that Jazz.

How about this:

Name: Warbot or something
Size: I don't know, something like 4 times as big as Jazz. Bigger is better.
Attacks: I don't really know, something like 2 rocket launchers, two guns that shoot, etc.
Abilities/equipment: has a jetpack(so he can fly)
How to beat him: He's kind of like a piece by piece boss. First you blow up his legs, then his arms, then his rocket launchers, then his jetpack. After that, he could be defenseless(so you can kill him easily) or unleash a fury attack that just makes him harder than he was with all his appendages. You finish him off by blowing up his body.
Appearence: Large, grey, looks a little like something from MechWarrior.

What do you think?