Halloween III was one of those horror movies I never thought much about or cared for because it had nothing to do with the first two. (Although when I was a kid the Silver Shamrock song was pretty creepy, and still is).
But probably about 15 years or so ago I found the DVD cheap and thought, "Eh, what the hell," and bought it just to add to the collection. I finally decided to give it another go and watch it not as a Halloween sequel but as it's own movie.
I've got to say it wasn't as bad as I remember. Not great but also not really guilty of all the bad reviews. Definitely one I'll probably watch again during one of my horror marathons this weekend. I'd give it about 6/10.
As far as the original plan....that could have been interesting. I didn't mind 4-6 but doubt I would have been too upset had they not been made.