I think a geodesic sphere is well suited and perhaps too much concern is being paid to light weight. Two points:
* Does the pressure per square unit differ depending on sphere size? For instance, if a sphere has X radius with a given pressure per square meter, does that pressure per square meter differ with a sphere of say, 10X?
* Can a geodesic sphere be made larger without increasing the size of the base triangles? Using the above example, if the base equilateral triangles have strut lengths of 1, the larger sphere could have the same. More triangles, but base triangles of the same size.
My point is, if the base triangle can withstand the pressure, good things happen with larger spheres. There'd be a beneficial trade-off between surface area (weight) and volume. However, if the triangles were made larger, the covering and struts would have to be made stronger.
