Trask is out of the equation.
Franks can get us thru the next two games, playing EJ is an option but not a requirement. As noted, Toney can play backup for either (or both), and/or we can thrwo more wildcats with JS/LP in the backfield (utilize the running game more). EJ is an option, playing him is ONLY for his benefit, not anyone else's, nor the team's. Maybe for recruits, but are we really bringing any kids to the Idaho game? C'mon, man.
Those claiming EJ time against Idaho is great game speed practice...I disagree. From a coaching perspective, EJ should do well against them, they really shouldn't be much of a challenge for him. So, he gains meaningless snaps. However, because it is Idaho and he'll look great, you now have a louder fanbase clamboring for EJ (anyone, really) to start ahead of Franks, whom you are depending upon for the next several games. Bad coaching move.
Given he has 2 games to retain the redshirt, it should be F$U and the Bowl game, IMO. Idaho is NOT worth wasting the redshirt. I get folks believing he won't be the starter the next few years (he leaves early, he gets surpassed by a younger, better QB) but those are what-if scenarios. I'd rather have his availability all those years than lose one of them over a meaningless game against Idaho.
Showcase EJ against F$U, show the recruits freshman get meaningful time, against rivals and games that matter. Have EJ in a good portion of the bowl game (depending upon who we get as an opponent, it may be less...or more...that the F$U game) - but show recruits freshman get meaningful time in the bowl as well.
It makes no sense to burn the redshirt against Idaho. None.