I was more thinking along the lines of later VTOL designs like the Phoenix and DC-X wich all had more or less short and stubby biconic shape,
IIRC, the first and second stage tanks are made in the same factory using the same tooling. Varying the length is easy. The diameter, not so much.
DC-X had an conical aeroshell over cylindrical propellant tanks
That also applies for all the handling equipment, GSE and facilities (pads, test stands, etc). They are all set up for the current diameter.
QuoteDC-X had an conical aeroshell over cylindrical propellant tanks Yeah right...
But you'll notice that the aspect ratio is still pretty pencil-like for the ones that aren't moved that way (aerodynamics). Drag increases with area.
You might want to reconsider that opinion.