"[Gholston] gives us another guy at defensive end," Dantonio said before practice. "He’s been toying with things back and forth -- you see him in pass rush drills and in linebacker drills. He came over and sort of poked me in the back on Thursday at Ford Field and said, ‘Hey, Coach, I want to become a defensive end permanently.’" [ . . . ]
I still think Gholston may ultimately have more promise as a rushing linebacker -- and the move today obviously doesn't preclude the coaching staff from going that route in the future. But for the moment being, the move makes quite a bit of sense, particularly if Will has designs on contributing this season (as I'm sure he does). We're all aware that MSU is stacked at linebacker this year, with the best unit in the conference. Gholston could have seen time as an outside linebacker in blitz packages or simply as a change of pace, but it seems relatively unlikely that he would have beaten out Eric Gordon and Chris Norman/Denicos Allen for substantial playing time.
Defensive end, however, is another matter entirely. At the moment, Colin Neely and Tyler Hoover look to be the starters. Neely did a nice job last season--the game ending sack at Purdue was a particularly memorable moment--but in the end, he only registered 3 sacks and 24 tackles. Tyler Hoover brings substantial athletic ability and size (6'7", 270) to the other end position, but he is inexperienced. The depth at the position isn't the greatest, either. Adam Rittenberg noted today that the BTN analysts attending MSU practice last week weren't exactly blown away by the defensive line's performance (save for Jerel Worthy, obvs). This comes after a season in which the line consistently struggled to pressure opposing quarterbacks, which necessitated linebacker blitzes and left the secondary hanging out to dry over and over again.
So, there is an opening and a need for an edge rusher, to say the least. It's perhaps unreasonable to expect Gholston to step in and be the guy right away, but he was hyped for a reason (i.e., size, quickness, and strength in spades), by all accounts he's looked great in practice so far, and he's clearly not shying away from the challenge. He's not going to be an every-down player at this point, but playing him at defensive end increases the chance that he'll be a substantial contributor here and now. After a season in which the defensive personnel management and playcalling was deeply flawed, the coaching staff at least seems to be batting .500 so far this year.
[Addition: And as DP99 points out, most of the foregoing assumes that MSU will still be running some kind of 4-3 on a relatively regular basis. Which I still think we will, for better or worse.]