I don't know. It's a completely different position. It's not like a different linebacker or line spot. It would be different if he'd tried it and we could judge.
Usually OLB converts are "tweeners". Good rushers who aren't as tall or as devastating, but have the ability to change direction, hit whatever. I am not a football personnel expert.
The tallest linebacker ever, that i can find was Ted Hendricks. He was the same height as Peppers, but at 220 was a lot different body type than a 283 pounder.
Covering running backs, changing direction, getting down for tackles, I think your center of gravity might come into play as well as other natural physics of a players 3-4 inches shorter. Our linebackers are heavier than most, but not 283.
I'd love to have a devastating pass rusher, in fact that is my number #1 desire for the new season.
Other than wishful thinking, what evidence is there that Peppers can make the switch others haven't been able to?
You kind of answered your own question regarding evidence. You seem to be focusing on measurables that in the grand scheme of things really mean nothing. Height/weight type stuff is nice to look at for a frame and body type, but it has no real bearing on how a guy plays. Triple Option is dead on about the transition not being the most difficult in the world. He also knows more about football than the other guys posting on this thread combined, so his word is best taken well.
In my mind, there are a few characteristics that a player needs to have to move effectively from a three point to a two point. The first is a football IQ. You have to have the vision and the aptidue to pick up on what is going on around you. To know your assignments, to read multiple keys and be able to recognize misdirection and playfakes. You have to be able to press and run with a tight end while still reading the qb. 43 ends don't have many cues to read and not a ton of assignments. A running joke I had with my ends is that an end is like a linebacker, only taller and stupid. The second most important in my mind is hip fluidity/foot speed. Typically, ends have pretty tight hips which is a major hinderance in the transition. Not to state the obvious, but playing linebacker is all about keeping your shoulders over your knees, staying square to the LOS and fluid in your direction changes. Think of it like the inverse of how a tank moves. The treads stay relatively linear, the turret is constantly on a swivel. Basically, you need to be able to open your hips, drop and accelerate without any wasted motion. You need to be able to move from backpedal to a sidestride to dead sprint without hesitation. You also need to flip your hips over after your blocking read, drive quickly into a zone, plant and accelerate to the ball all within five or six steps, generally speaking. As a rule, you are going to be a step slower than most tailbacks and the only way you will be effective in covering them is by not wasting any motion and gaining acceleration in and out of your breaks (that, and grabbing jersey for a quick tug or holding their arm for a second to screw up their cadence). Linebackers are only as good as their hips. The footspeed of a player is the catalyist for all of this fluidity. Any player that is going to be effective inside the box needs to have tremendous foot speed to be able to wade through traffic, disengage blocks, pickup and cut with a reciever and finally close to the ball to finish the play. While these are two different attributes, they all combine to be the utilized athletic skill. Last, the player needs to have a bit of a nastyness to them. Linebackers need to have a certain demeanor of feeling insulted. They need to really dislike the oponent, take it personally when they are blocked and get to the ball at all costs.
Put these all together and you get a highly effective linebacker in my estimation. In the games I have seen Peppers play, he has shown me rare hips for a player of his size, outstanding footspeed and handwork, enough football IQ to be a captain and diagnose many plays from the backside and a bit of venom to him as well. The fact that he wants to be in a 34 means he understands the game of football. For a linebacker, the 34 is the most challenging and rewarding defense to play in. You truely are the most versatile weapon on the field, you get to play all over the place. In the case of Julius Peppers, the opportunity to play for the greatest 34 mind ever.
RC, if you evaluate a player for a conversion you must follow a simple set of rules. Look at your scheme, look at the player, look at their scheme, look for the synergy and finally evaluate. If one were to focus more on the attributes of the player and less on the attributes of the defense, a better view of the fit would be presented.