Forest's striking is definitely an asset, not a liability. His huge reach a rugged chin make his stand-up hellish for opponents. I just can't see what happened to Liddell happening to Forest, precisely because he's not explosive. He's more like a tough piece of wood. A lot of the light heavyweight contenders are explosive fighters, which I think plays to his strength. He's a take-the-wind-out-of-your-sales kind of guy.
I definitely see Brock as the most vulnerable champ right now. There's a man with a lot of holes in his game, and who recently lost to Mir, who could very well be his next opponent. Then again, I don't see any champ getting a tougher fight than GSP in the near future, even if odds are in his favor.
Of course, a Silva/Griffin title fight would undermine everything I've just said.