I can see why that would appeal to Ferguson, who's been linked before with Delph.
However, as John83 points out, I couldn't see it appealing to Gibson. As it happens, Fergie tried to persuade Gibson to go to Peterborough U, where his son Darren is manager, at the start of this season, but Gibson said "no".
Iirc, "personal terms" were said to be a problem, although I suspect that Fergie Sr. would have found a way of smoothing that out to help his son etc, so it's more likely DG didn't want 3rd flight football. Of course, Posh have since been promoted...
As for Cathcart, he ended going on a season-loan to Plymouth Argyle where, despite the club struggling to stay in the Championship, he went straight into the team and stayed there, apparently playing very well (Fans' Young player of the Year).
Unfortunately, because his career path has shadowed Jonny Evans (e.g. both spent time at MU's feeder club in Belgium, then went to a Championship club on loan), peoples' expectations of Cathcart are very high, perhaps unrealistically so, for JE is such a hard act to follow.
That said, CC was Captain of MU's Youth team, and when FIFA picked a European Youth Select XI to play their African Counterparts in Barcelona a couple of years back, Cathcart was the only British Isles-born player to be selected. Also, he's the NI U-21 Captain, where he's the backbone of the defence.
http://en.wikipedia.org/wiki/Craig_Cathcart
Coincidentally, he was MU's Young Player of the Year (Jimmy Murphy Trophy) the season after Darron Gibson, with Welbeck being his successor, followed by Macheda this season.
http://en.wikipedia.org/wiki/Manches...rs_of_the_Year