ORIGINAL: Tired Old Man
Some will argue to the contrary but my experience is no, there is no problem as long as you follow established procedures avoiding metal to metal linkage contacts and secure the cap correctly to the plug. I would not go out of my way to lay the spark plug cable on top of the servo, but generally there are no problems.
My small 30 size YAK has the ignition battery on the left side of the motor box, the radio battery is on the right side and the ignition module is on top. Throttle servo is inside the box close to the firewall. All wiring dresses in different directions and none of the wires cross each other. Works great!