What about having Bruce Carter shave ten pounds to play strong safety? Tall, fast, great jumping ability. He would be a ballhawk!
This is a rather familiar premise going back to the Roy Williams era. When Roy was a safety here with tight hips and poor cover skills, but wonderful hitting and solid play in tight spaces near the line of scrimmage, the popular idea among fans was to convert him to LB. Further, Bill Parcells didn't help things when he would describe Roy as "a biscuit away from being a LB".
The trouble is that moving up the size ladder is sometimes possible. But, moving down the ladder is very rare.
Imagine a ladder with the lightest players at the bottom and the heaviest players at the top. You never see a FB moving down to be a RB, or a Safety moving down to CB. But, when a Corner gets too big, we move him to Safety. When a WR gets too big, we move him to TE. I am not sure I recall a TE who moved out to WR. Speed kills in football and a fast TE is still a very slow WR.
And a fast LB would be a very slow Safety. It cannot be measured in straight ahead speed all of the time. Sometimes, their 40-time will be very similar, but then we get to stop and start, hip tightness that does not allow for change of direction, lateral and backwards speed, and so on.
Let's look at the size of Inside LBs Dallas has in the 3-4 defense. Keep in mind that the 40-time will be from their NFL Combine before their respective drafts (no, Keith Brooking is not able to run sub-4.6 anymore):
As you can see, Carter is fast, but not so fast that you see him out of the realm of his contemporaries. In fact, OurLads.com has him at 4.6 and because he did not run at his combine, there are many different 40-times floating around for Carter. Trying to decipher what is true and what is legend (one site suggest he was in the 4.4's) is not always easy - especially when a player is coming off ACL surgery. A source with the Cowboys believes that 4.55 is a fair number.
So, could he play safety?
Here are 5 random "Strong Safeties". Some are thought of as premier, some are SS that the Cowboys have tried and have not enjoyed success. And then there is Atogwe, who I thought the Cowboys should have targeted back in February - but ultimately signed with Washington.
Surely, everyone can see the size and speed of these players. To the naked eye, LB and SS may not seem that far apart. And they have many of the same responsibilities but in the NFL, those similarities are not redundant enough to think you can ask a LB to shed a few pounds and suddenly have the lateral and backward quickness these players need.
And, remember, don't get caught up in 40 speed. You see the claim that Roy Williams could break 4.5 in the 40. But remember how tight his hips were? He could not turn and run at all - even with Tight Ends near the end of his stay here. A LB covering downfield is a disaster compared to a DB. The best downfield LB for cover skills might be Brian Urlacher in that Tampa-2. But, would you rather have him then a safety? No way.
Darren Woodson is one who inspires many Cowboys fans to look in this direction. He was 6'1, 219, and his 40 was around a 4.40 or so, although records back then are hard to find. He seems more the exception than the rule, here.
Also, in the NFL in 2011, the FS and SS are mostly interchangeable in that with 2-deep looks, a team wants to be able to ask both to do each-others' job. So, are you ready to have Bruce Carter play CF against Aaron Rodgers? Of course, not.
I see where you are going, and the Cowboys think they have a superb athlete in Carter, but a superb LB is a tight hipped, tough-to-turn Safety in the NFL that opposing QBs would attempt to attack.