At this point there is only a sliver of fans who want Reid to return, naturally we all have our own favorites for the replacement.
Mine is Chip Kelly.
Currently Kelly has his Oregon Ducks sitting at 9-0 and if they run the table they will likely place themselves in the top 2 to play in the BCS Title game (thanks to a backloaded schedule). Thus far in his tenure, Oregon is 43-6 with 3 BCS bowl game appearances, obviously headed towards 4-4 in that stat.
Kelly runs a spread offense, so obviously that would need some tweaking, but not as big of an adjustment would need to be made now versus a Steve Spurrier in the earlier 2000s. The NFL is a different game now and variations of the spread have found success in the league. His system is actually run-based, which would offer a nice change from the current regime.
Kelly is clearly an offensive specialist (even though he spent 1 year as a DC at a smaller college), and that reminds me of simpler times of Reid when he didn't try to work with the defense. As far as OC, Kelly should just bring in his own guy so there is no need for speculation there. I want a coach who does 1 thing and hire someone to run the other side, in this case he would need someone to take defensive control.
Some candidates I would like to see there would include (among others):
-Mike Singletary (Fmr HC; MIN LB)
-Raheem Morris (Fmr HC; WAS DB)
-Kris Richard (SEA DB)
-Winston Moss (GB LB)
There are definitely more to consider. Personally I would lean with someone who had HC experience because to me those are the best Coordinators you find around the league, so Singletary or Morris would represent examples of those, but some of the top young assistants like Moss (whom we should have hired in 2011) or Richard, who has one of the best running units in the NFL right now (press corner heaven) would be fresher picks.
Concluding, Kelly is a bright offensive mind, he's under 50, he WILL get an NFL job this off-season or next (would be TB's now if he didn't want to chase the BCS tittle again) and would be a completely fresh change of pace from what we have had for the last decade and a half.