A concept for the Nova class starship, from pg 178 of the Tech Manual:

    Still another advanced starship concept would call for
variable-geometry warp nacelle pylons, permitting optimization of
field stress during extended Warp 8+ flight, resulting in
significantly improved engine efficiencies. This design study
features a saucer section composed of wedge-shaped modular
segments that could easily be replaced as mission demands change
and new technology becomes available. This concept calls for an
internal volume approximately 40% less than the present Galaxy
class starship, but is expected to perform similar mission
profiles within normal cruise ranges because of the relative ease
of spacecraft segment swapout.