The only thing I can think of is if you put a large structure in the center creating enough space for the large cats to swim around, you can bisect the tank into two large sections. Put some structure in each corner and let each pair of pikes make that the home base. You can get some viney plastic plants from A craft store and attach the bases of them to each of your structures to create more sight line breaks and have them rooted high enough on the water column to not interfere with the ground space.
What I'm imagining is sometime like this. With the tank being a rectangle, put right structures in each corner shaped like a right triangle and put an isosceles triangle shaped structure in the center. Actually just left or right of center will look more natural. Let the floating viney plant speed out a bit too to lengthen the shaded area around the structure to ensure your pikes treat the structures as their home.
It's tough to try and create mid water or top water structure with such large cats on there that can knock them over. Also, most pikes tend to choose bottom oriented structure in an aquarium.