It's no secret that I loved "La Reconquista" and its novelization, so I'd love to see that get an animated film adaptation. (An animated film version of the recent Nogizaka46 musical could be cool as well.) I also think the planet Grimm subplot in the Mistress Labyrinth musical could be fleshed out into a 60-minute anime film.
But as far as doing a whole "series" (or season) goes... the Dracul arc (being an arc spanning four musicals) is the only musicals-original concept that could sustain a multi-episode animated adaptation.
I think the Dracul arc could have actually made an excellent 6th season of the 90s anime. Of course it would have to be heavily edited to avoid plot holes with the 90s anime like for instance Undead Berserk could not be Professor Tomoe as it would just be reductive to have him possessed again. Maybe he could be a rival scientist and Professor Tomoe could aid the Senshi against them. Obviously the Samael Quartet stuff would have to be removed as it contradicts the Amazones Quartet's story in the 90s anime all though they could bring back the Amazones Quartet as the Sailor Quartet and have them officially become Sailor Chibi Moon's Guardians. Another plot this one Sailor Stars musical where it followed the plot of the 90s anime but had an additional part that after Sailor Galaxia was freed of Chaos that Chaos went to the Galaxy Cauldron and corrupted it. This could have made an excellent movie for Sailor Stars where maybe Sailor Moon, Tuxedo Mask, Sailor Chibi Moon, The Inners, Outers, Sailor Galaxia along with Sailor Kakyuu and the Sailor Starlights go to the Cauldron to fight Chaos and maybe could deal with some of the manga and Sera Myu Stars villains as enemies it would also be cool to see Sailor Cosmos in the finale who of course would not be Chibi Chibi in this version.