Alright, I looked into this a bit with some help discussing and researching from peers.
"After you execute a maneuver, you may gain 1 tractor token to perform a rotate action."
Baseline, a ship cannot perform actions while stressed unless an upgrade card or ability explicitly states being able to while stressed. Nantex ship ability doesn't explicitly say the rotate action can be taken while stressed, therefore, to perform the rotate action, it must not be stressed.
Next, under "Paying Costs" in the rules reference it says "A ship can pay a cost for an effect only if the effect can be resolved." That means that the Nantex CANNOT gain a tractor token while it is stressed because it cannot complete the perform of a rotate action from the ship being stressed restriction. The cost being "gain 1 tractor token" and the effect needing to resolved being "perform a rotate action." The keyword in the "you may gain 1 tractor token to perform a rotate action" is TO as it's not a may type that would make it optional allowing the ability to just gain a tractor token to give you an option of performing a rotate. It has to be able to perform a rotate action to be able to gain the tractor token.