I know the NBA is not about being nice, but if I was Jimmer's agent I would say the following to the Kings front office.
If you're gonna keep Jimmer and not start him you should pic up his option. This gives him two years for serendipity to run it's coarse and get him the PT he needs to show his value e.g. injury, roster changes, etc.
If you aren't gonna sign his extension please trade him to a situation where he can get the playing time he would need in a contract year or start him to give him the time he needs now. If you keep Jimmer and don't sign his extension, and then don't play him, it seriously effects his money making potential, if I'm an agent and I know Jimmer has helped Sacramento's bottom line in Jersey sales, ticket sales etc. and I want the paycheck that Jimmers next signing could mean, I'm forcing the trade or the playing time, leveraging my other free agents, representatives etc if I have to.
From a pure basketball perspective it is absolutely fair for either Thornton or Fredette to sit the bench, they have both done enough to make a case for each one of them as a starter (Thornton has good pre-season numbers and better regular season numbers, Fredette has better pre-season numbers and fills up a stat sheet with more than just scoring).
I totally understand that B-Mac will get his minutes (A strong case could be made for him to start as he is the best two-way player of the group, but I think Malone has a good development plan for him, and think that includes him starting at some point this season)
I would personally like to see Jimmer start, see what he can do and have them not sign his extension, build up his worth and flip him for assets. I would then put B-Mac in the starting role, and have Thornton back up B-Mac with the other McRookie as the third guard mixed in with IT and GV in case of injury etc (IT actually plays the two pretty well with GV) that would be my plan.
Why would I roll with this plan instead of starting Thornton? Thornton is a known entity and is going to be a hard contract to move this year, people would rather have him next year as an expiring contract and in a contract year (Great motivation). Jimmer is still an unknown, so I'd give him the time he needs to be a better known entity, not sign his extension, and then flip him for something the Kings need (Please a SF).
Pure basketball again, IT works great in a very classical sense with B-Mac. B-Mac has the height to defend the two of the league and the quicks to keep up with IT. B-mac is a shaky handler so far so IT helps out a lot there. If i'm the coach I let GV start until B-Mac is ready to make the switch, I then move IT with him to the starters.