I have seen a couple of custom ukes that have the tuners "staggered" a bit. Do all four tuners have to line up even horizontally across from each other? What would be the reason or effect to have them staggered?
They can be anywhere the builder likes as long as they still function well. I've even seen them with three on one side and one on the other, sometimes all four will be on one side (Fender style.)
You see, even something as simple as staggering the tuners improves the aesthetics a millionfold. Uke builders of the world, design doesn't stop at the nut!
So long as you have a relatively straight path to the peg from the nut it's all good. The other guys will be able to tell you better than I if break angle from the nut is more of a concern on nylon stringed instruments, and particularly Ukes. I'm strictly a steel string dude.