So if we step back a second, look at a Ringworld. I'm not sure if Larry Niven proposed this idea (in the book by the same name) or just popularized it, but the idea is basically this: If you take the mass of the Earth and turn it into a ring that encircles a star, spin it to create artificial gravity and put walls on the sides (on the inside) to keep an atmosphere in.

What do you have? The same mass of Earth will have a million times the living area.

What's the problem? At 1 AU distance, this thing would have to spin so fast (IIRC ~1.5 million km/h) that the centrifugal forces would tear it apart. Not even graphene could withstand the forces. So the idea just isn't practical.

So if you create a hard shell, you have to ask: what is the intended goal?

If there is to create living area, where is gravity coming from? Do you spin the sphere? If so, it has the same centrifugal force problem.

If it's not (and technically even if it is) then you have the problem that the shell will collapse under the gravity of the star and/or its own mass.