I think that a number of people have followed on your lead on this topic... and by and large I've always sort of liked those approaches.
My personal pref would be to evolve from the Discovery to the Daedalus, and to evolve from the DY-100 to something very closely resembling the Hyperion class heavy cruiser in Babylon 5, and let the small disk on the Hyperion grow into a saucer-shaped primary hull. Eventually, the two design lineages would MOSTLY converge.
Of course, there's no reason to leave the "NX-01" design entirely out of the lineage, either... just "dumb down" the technology a bit, change the appearance slightly (not necessarily even change the basic shapes or configuration, just the surface detailing and the finish) and I'd have no major issue with the NX-01.
So, we have a "flying saucer with side-mounted nacelles" in the NX-01. We have a secondary hull with a tiny "precursor" primary hull in the DY/Hyperion lineage, and you have the "big primary hull" with the Discovery/Daedalus lineage.
I'd be interested to see a "discovery-ish" design with a significantly larger sphere (but still with an internal centrifuge)... say, three or four times the size. With a trusswork/modular "spine" moving straight backwards to a very "discovery-ish" engine section... but with the whole spine/engine thing offset downwards by a bit to give a balanced design (masswise) to compensate for a pair of crude warp engine nacelles offset to either side and slightly above the secondary hull/"spine" section. And the spine would be a bit shorter (relative to the overall size) than the Discovery's spine... say, 2/3 the length.
The DY-path would move from the existing DY to a larger design (as I said, resembling the Hyperion) with a pair of warp nacelles coming off, straight to each side but trailing behind, near the back of the ship body (where the DY has its "solar fins"). The "conning tower" on the DY has a little bump... this would become a small disk (ala the Hyperion). the dish would become larger over time, of course. This lineage would eventually result in the Baton Rouge class (see the Starflight Chronology as the original reference).
There should be other design lineages as well, unrelated to ANY of the above three. Eventually you'd converge on the best solutions, but you'd still have variation from ship purpose to ship purpose.
Anyway, that's my 2cents...
