I think that whimsicott is a much better alternative than a Cloud Nine Pokemon, or even Galarian Weezing if you ask me. All the Cloud Nine Pokemon don't have the best stats, plus they are all weak to fighting moves (except Golduck, but Rillaboom is #1 in usage, so...) which are pretty common on a lot of threats like Tyranitar, Cinderace, and even Rillaboom sometimes.
However, I don't think that Utility Umbrella + Switcheroo is really necessary, as most weather abusers are Swift Swim, Chlorophyll, or Sand Rush, which doubles their speed, and whimsicott can set priority tailwind for your teammates, effectively negating both speed boosts. If you really think it's valuable to take away their item as well, it might be useful, but it could be a dangerous game as a lot of Kingdra run specs. It would also be better for Sand force excadrill, but I haven't really seen that at all.
Overall, it's a funny gimmick that could potentially be useful in certain situations, but as tailwind does almost exactly the same thing, so you're probably better off with a different support move and item.
Hope I helped!