First off, you won't be a civilian contractor. You'll be a civilian employee to the government. Big difference in that you won't be beholden to contact renegotiations and other instability. Govt civilian has it's pluses and minuses. It will be interesting to see how they manage these people as the civilian structure is much different from the military structure to include performance, feedback and removal from positions.
Will you be shit on as a civilian? This is a complicated question. Will you get work the mil guys don't want to do? Depends on how they write the position. Will you be respected by students and other IPs? You'll definitely have an uphill battle to earn respect as an IP. You'll be missing the "been there done that" of the military in general. I would imagine students will avoid going to these guys for mentoring and insight as they will not be relevant for military flying outside the few T-6 hours gained at PIT.
That said, if you can be humble and do the job for what it is, you'll probably have a great time doing something your peers won't be able to do. No reason to pass on it if your motivation is purely for the flying experience.
As for bailing for the guard, I haven't seen a civilian position come with a commitment and I don't know if that's even legal. If you don't have a contract, you can pack your bags at any point.