I just asked this question on MathOverflow. It's basically idle curiosity, but I've now been idly curious about this for several years, so I figured I might as well ask it publicly. Please let me know if you have any thoughts!
In short, the question is: Do every two smooth projective curves over \(\overline{\mathbb{F}_q}\) of genus at least \(2\) have a finite etale cover in common?
See the question for more details and remarks.