I'm inclined to go for either the Blister Deflector or the full secondary hull with deflector - we picked Full Saucer for a reason, after all. That, and it'd allow for additional capability in terms of shuttlepods for surveying and exploration, enhanced medical and biological research facilities (useful if we need to press this thing into service as a hospital ship, or to research unique lifeforms/biohazards found on surveyed planets), etc.,
We can give it vertical shuttlepods, but I really think we should avoid scope creep for now.