Coleman is not a 4 for those saying he can play there. He will either start at the 5 or back up Melo at the 5 if Melo stayed (highly doubtful).
You are exactly right. There has been some confusion as to why Noel is considering us given he will have to compete with other big men.
Noel is equally adept at playing the 4 or the 5, he has the quickness of a 4 and the presence of a 5 in the paint. If we sign him and Melo leaves the battle for PT will be between Coleman and Christmas to see who will play along side Noel. If its Coleman, Noel will play the 4 (there is no way Coleman is going to cover the wing of the zone). If its Christmas, Noel will play the 5. Of course, with three guys to fill two positions, all three will get starters minutes (much like it is with Jardine, Triche and Waiters right now) so it really does not matter who starts and who comes off the bench.
If Melo does stay, it will not affect Noel's playing time at all. He will simply move to the 4 and start. The guys who will be affected in that scenario are Christmas and Coleman who will go from playing starters minutes to playing back up minutes (maybe 10 minutes a game each, with a chance that one gets 20 and the other drops out of the rotation).
I will be very happy if we end up with either Melo or Noel. In that scenario we will have an elite shot blocker and an opportunity to red shirt Keita - which I think will do wonders for his development.
The one thing I am confident of is that Noel is not worried about battling for PT. No matter what scenario plays out, he will be the starter and play major minutes. There are many reasons he might go to Kentucky, but fear of losing PT at SU is not one of them.