My guess is that the coaches are asking the same thing right now.
One thing going for him, is that he plays receiver and hypothetically can be a returnman/special teamer too.(He would not be ready in this offense as a tight end, a safety, lineman, or linebacker to do what is required for our offensive scheme. Honestly the two positions that suit freshmen in this offense would be receiver and Dline- traditionally corner is a position that truly amazing athletes can play early at other schools, but at BYU, this might not be possible because of the scheme and zone defenses they have to learn).
This is not the toughest position to play in the spread and certainly he can be used to keep a defense honest. Even if he really does only run a 4.7, he's big enough that a smaller DB would be stupid to give him a 15 yard cushion and then make themselves responsible for tackling him.
What remains to be determined:
1. How Chambers will adjust to BYU Campus, the environment, and being a college student at a relatively high functioning level.
This is not a kid that has grown up in Utah Valley and has spent as much time at the BYU campus as they have at their own high school stadium. The culture shock has to be considered. (maybe football helps get over that, maybe it overwhelms him)
This is where Missouri freshman Tony Temple stumbled and Missouri blew an extra year of eligibility on 13 total carries. (The same kid that rushed for a Cotton Bowl record 284 yards last year, runs a legit 4.35 40 and is considered too small to play in the NFL everydown- He would have made Missouri a legit national championship contender next year. Yet Gary Pinkle got greedy and put in a completely unprepared frosh, blowing his redshirt)
Obviously we don't want to risk the same thing with Chambers. If he's not 90%+ indoctrinated in BYU life, freshman living, college, etc. then personally, I say redshirt him.
2. How are his hands and ability to get off the line? (Based on the difference between high school and D1 level college, a lot of freshmen don't catch everything thrown at them or have the know how to get separation).
If he's dropping a lot of balls in fall camp, redshirt him. If regardless of his size or arguable speed, can't make room to bring in balls, redshirt him. Unless you're Rod Wilkerson, you can teach good athletes how to hold onto balls at the D1 level and how to create separation (Kevin Curtis comes to mind as a guy that mastered those things as a student of the game).
If Chambers is the second coming of Michael Crabtree (which would exceed all of my dreams and force me to immediately purchase a Chambers BYU jersey) then it's a no brainer - - play him and let Collie know that even "clean living" isnt' going to get him 100 catches with Chambers on the same team. Who knows, I don't think anyone expected Crabtree to be the 2nd coming of Jerry Rice......(Yes, he's that good)
3. Do we benefit more from having a Chambers/Jacobson/Hafoka/Ashworth (Collie+1) group for 3 years together; maybe a better way to ask-- is Michael Reed the answer this year as the #2 option. If Reed is the man this year, then why not use the bevy of potential backups and 3rd stringers (Koz, White, Ashworth, Hafoka) and save Chambers?
4. Can Chambers return kicks and punts effectively? This question may trump everything else. If the answer is yes, Collie is now saved for what he needs to be doing; and potentially G Pittman is also protected from injury. Mahuika becomes the 2nd option at returner (not a bad 2nd option) and can concentrate on competing for backup receiver minutes.
Mendenhall has not been shy about using starters and youngsters to return balls.
5. Do we risk upsetting or losing Chambers psychologically, emotionally or football-wise by not playing him? Every coach has to ask themselves that when considering a redshirt, some freshmen absolutely need a redshirt, others are more of a risk to themselves and the team by being redshirted and not having the full connection with the team and football. This has to be considered.
6. relatively unimportant - Chambers has friends that will either be on missions or at a JUCO that want to play at BYU. (Apparently even Austin Holt and Chambers have a great relationship) redshirting him, gives him the chance to play more with them.
7. Bottom line? Do we need Chambers to increase our chances to go undefeated and get a BCS bid. (obviously this is a combo of all the considerations) If the answer is yes, and the risk to Chambers psychologically is low, then play him. If our team isn't substantially better with him playing, then why blow a year of eligibility on a guy that has a chance to be a flagship player in the future?