I'm echoing the "filler" explanation. Little Planet's design might have been sketched out at the start of planning phase when the team was still deciding on level themes, so the presence of features like cacti, mountains, and volcanoes doesn't immediately signify deleted levels.
KingofHarts, on 18 June 2012 - 12:40 AM, said:
Well, it needs to be taken seriously... That would be awesome to have something new in the game... Someone could do it and get the R2 folks to shut up. I'd love it at least for a hack.
Final Fever... shouldn't be a zone in itself though. I always thought that was just a name for the music in the final boss.
I don't see how an entirely fan-imagined version of the level is going to make anyone "shut up". It would be interesting to see, but it'd never be authentic, and would put us no closer to seeing what the developers had in mind for the level. But I'm not convinced that they ever made nearly enough content for a fully fleshed-out Zone anyway, and what they did
design was likely not of the highest quality. I recall hearing at one point—on this forum, in fact—that Sonic CD's early development was split up between small pieces of the team, each responsible for planning and drafting a single Zone, and that R2's team was behind schedule, not meeting quality standards, or something to that effect, and the level was cut during the planning phase. I think the only thing we know for sure was that they had decided on a ruins theme for the level, as seen in the credits' infamous deleted scene.
Sure, we all want closure on the R2 debacle, but "Desert Dazzle" would have just felt random and out of place with the rest of the levels appearing just as they did in the original game. If I were Taxman, I'd have dropped it too once Sega professionally green-lit the project. As for adding a level via modding, I still don't think it'd be worth it. Sonic CD is in many ways very distinctive, and such a level would be far better off in an original project. We have no way of knowing what the original team would have done for the level, and we may never even see the scraps that remain, if they've even survived to this day.
As for Final Fever, I'm fairly sure it was meant to be a single-act Zone directly following Metallic Madness act 3 where you would fight the final boss. Sonic CD re-imagines all of Sonic 1's level tropes (Marble excluded, but that's likely where R2 was to come in) and Final Fever would have been the parallel to Final Zone.