The screw modifier is good for creating a solid mesh from a single curve profile, but it does not seem to provide any options for handling multiple curve profiles.
This is the result of using a screw modifier on two (asymmetrical) curves. The generated mesh does not line up at the seam, since the two profiles generate independent submeshes.
Can the screw modifier interpolate between the two curve profiles as it rotates around and creates each vertical slice of the mesh? The dimension of interpolation should be the radius of any point on the curve, measured from the central screw axis.
A result with clean topology would be a bonus, if possible.