Observer mode

[GooglyBoogly]

because just getting a tinker and watching the game is the same thing,

No, it isn't. The observer player will get their share of the force gold, and thus weaken their team. The tinker will also get killed in the late game when their base is pushed, providing further gold imbalance - the pilot, doesn't have that issue - but you'd have to keep using the pilot TP ability to prevent the AI from taking over.