So it would be kind of like the Champions League?
I don't believe that it is possible for the highest tier of a domestic league to contain sub-divisions, due to the necessity of allocating qualifying places for the relevant continental club competition. I also think that the editor will not allow it anyway.
Your best alternative would be to have your sub-divisions forming the second tier, and have an elite group in the highest tier. However, I would definitely recommend having 8 sub-divisions instead of 9, as this makes selecting teams for the playoffs much easier (as it is divisible by 8).
My recommendation:
--------------------
Tier 1 - Elite league containing maybe 8 teams, who play each other for the championship title.
Tier 2 - Comprised of 8 sub-divisions, each containing an equal number of teams, to keep it fair.
At the end of a season, the top 4 Elite teams (i.e. the semi-finalists and finalists) would keep their places in the top tier. 4 teams would then be relegated.
The top 2 teams from each sub-division would then enter a playoff. If you have 8 sub-divisions, this gives you 16 qualifiers, which is ideal for a knockout. Two matches later, you're left with 4 qualifiers who will win promotion to the Elite league.