The F-14 (A and B, have to check about the D) indeed have an autothrottle in the form of the Approach Power Compensator (APC). But this is meant to ensure appropriate angle of attack (and consequently glide slope) during carrier approach. There is no speed hold autothrottle.
I guess fighter designers assume that the throttle is responsive enough to handle speed through the seat of your pants even when refuelling.
That being said we do not have that kind of feedback in a simulator, and a speed controlled autothrottle would definitely ease things a bit for cross country flights.
So to make this short : there is no autothrottle in the sense you are requiring in the real thing, and feel free to implement it for your needs (this is open source after all).
Cheers
Enrique