Will this work?
What do mean will it work? If you mean will it hold the sign above the dome: I’m not sure. The sign looks big. How heavy is it. Wind on the sign may be a problem also. It would be best to find this out experimentally. I would make the sign as light as possible, attach it to the dome at pole intersections at the top of the small triangles (the dome is strongest at these points) and have flaps in in the sign to let strong wind blow through or make the sign of a mesh that allows the wind to flow through it. With a light wind porous sign it should work.