I mean control over absolutely everything, so nothing unexpected is ever forced on you unless you want it to. Control over other characters, settings, sounds, smells, everything around you. Do you want this? Why or why not? Do you think it's even possible? Is it healthy?

I think it probably is possible with practice. But I don't want it. I like having non-trivial challenges to overcome, and having unexpected things happen. I suspect that using such power would be harmful if it was done all the time, as you are displacing the subconscious mind in doing something it natually does, and I assume the natural function is something good and healthy. Of course, such a proficient lucid dreamer wouldn't have to exert this control over all his dreams. I think I'd be happy with just full control over myself (flying, running, clarifying the dream, stopping myself waking, remembering things, etc.).