I have a catwalk and actor/ puppeteer that covers about half my show, he has about 15 gags. The simplest gag he has is an airzooka- it works wonders.
he has the classic spider on a fishing pole, drop bodies, he triggers several boggarts, and as I am outdoor he has ropes rigged to several trees and bushes for bush shakes. He also controls a spider web drop, and does general heckling from above.
I would just build your show ignoring the catwalk, then work scares in where it intersects or where he has great vision (my guy has an array of door bell switches that activate lights and sounds). With 35 ft cielings you might consider a bungee scare from the cat walk.