What I think the WWE needs to do in regards to this type of talent is actually put them through a sifter. Just because they're big doesn't mean they're special, as we all have seen it a million times. There is no shock value. Granted, if you met these guys in person, you'd be surprised how big they are, but not on screen. Khali is an exception as he's big enough that he really does look enormous despite how often we've seen it.
But what I mean with the sift concept is to actually study who can do what. Take for example your mentioning of Mike Knox. I don't mind seeing him wrestle. He's more entertaining than the likes of Snitsky and Tomko and whatnot to me. But Knox has nothing to his name right now, and no quick fix is going to solve it. If you just have Knox come out and start a program with Cena, he'll do nothing but job to the main event people from now on. That's not how you use him to his worth. Knox right now could be a legitimate threat to the IC title. Don't rush him into the main event cause it won't work.
Another person is Kozlov. This guy went from squashing local jobbers and Jimmy Wang Yang to having matches with HHH...and it failed miserably. Why? Cause he wasn't ready for it and he doesn't have the look of someone who could be the main event monster guy. But say we had Kennedy as US champion instead of Shelton right now - or if Shelton was a face. Wouldn't Kozlov make sense moving up the ladder and becoming a viable US title contender? Hell it would even make sense for him to win it. Then someone finally ends his undefeated streak (whilst winning his US title) and boom, you've got a face who is being pushed very hard (WHEN HE'S READY, mind you).
The problem with the monster gimmick is that its fireworks. It takes a long, boring time to set it up, you have a few pops here and there, and within a few minutes, its over and nobody cares. The monster always has the same assembly line path. You dominate jobbers, you start to dominate midcarders, you make it to the main event where you either beat the champion and have a successful reign on top (ala Diesel/Yokozuna) or you lose to the main event guy to make him look good (ala Umaga/Khali), and then you flounder around until you turn into a comedic face and lose to the next guy they're building up as a monster. Then you're released. Within a year usually, you've run out of steam, the fireworks are over, and everybody goes home.
So all in all, the only way to avoid that same boring path is to actually keep people at levels where they can be expected to both win and lose. Too many "big and unstoppable" wrestlers make their way to the upper midcard and we see them lose to the likes of your Batistas and HHHs and Undertakers, but then the week afterwards, the WWE has to "remind us" that they're big and bad by having them defeat a no-name in a squash match. Think about how many times that happens. Big Daddy V would lose to the Undertaker on Smackdown Friday night and then next Tuesday, he'd destroy someone like Stevie Richards. Helps his credibility a tad, but nobody forgets that he "will never win the big matches".
Let's take a look at another guy the WWE has right now: Ezekiel Jackson. In my opinion, they're working him well. He's dominated everybody he's been up against, but he hasn't been rushed into losing to Jeff Hardy or CM Punk to make them look good and give them a cheap and quick little pat on the back. Ezekiel could follow the Diesel path of becoming a tag champion, then a midcard champion, and then a main eventer, in logical progression, rather than going straight to the main event, losing, and being forced to drop down to midcard status.
Anyway, I'm rambling. Overall, the WWE needs to be patient with their big guys and utilize some of them specifically as midcard monsters and "the big guy in a tag team" roles, rather than doing what they tend to do and just take all of them and push them into the main event too fast. Knox and Ezekiel shouldn't touch the main event for a good while.