Not to pick nits, but I've noticed that a great many people on this site use the word theory without actually knowing what it means, and people using words they don't understand tends to irk me.
What this entire thread is about is conjecture, not theory. It starts with you making an observation (watching the show). Then you come up with an idea (hypothesis) based on what you saw in the show.
The problem is, nobody has ever seen the 9th chevron used, thus, no observation has been made. You can't form a hypothesis without observing something first.
If the show has never used the 9th chevron, any hypothesis anybody tries to come up with is nothing but conjecture (guessing).
A Theory is not a guess!
Theories become theories because they stand up to years of experiment and observation by others, not just the person coming up with the theory.
There should be very few times you can use the word "theory" and anything regarding stargate in the same sentence. The producers and writers change things, thus you can't ever have a theory that works.