Worth pointing out that Fev have a very small squad and I'd be a little surprised if Mark Campbell, who has pumped a small fortune into trying to get Fev into SL, allowed a first-team starter to play for Leeds if it weakened Fev's promotion chances, any more than Leeds wouldn't let someone play for Fev if they were required by the first team.
That said, when Fev signed Minns there was an interview with Steve Gill where he said something (can't remember the exact words) that suggested the door might be open for Minns to play for Leeds in some circumstances.
It's worth pointing out though that whilst top Championship players are often at a similar level to fringe SL players, there's a big step up to being a quality SL starter. At Fev we think Luke Briscoe is the best wing in the Championship, for instance, but most Leeds fans seem lukewarm at best (pardon the pun) about him starting for you in SL, same with Golding, who was outstadning in the Championship. Harrison the likeliest of our younger players that you might have your eye on long term as a project (Brad Day will miss most of the season through injury) but although he's already a better player than, say, Jack Ormondroyd or Josh Walters, I don't think he's better than what you have in your 17 at the moment.