So what i want to do is take away the green hag's spell like abilities and replace it with 6 effective levels of witch. the hag will have a familiar of a 6th level witch and will only have two hexes: evil eye and cauldren. the hag depending on how the CR is adjusted will take levels in the witch class to get it to the CR that i want for a type of early teen boss.
and second the only real spell like ability i want to give the hag is an at will polymorph.
so i was thinking with the hag being a 9 hd monstrous humaniod i would make its CR be around 10 or 11. is that close to its power lv??
Well, lets compare to other monsters with innate casting ability...
Coatl (12HD Outsider, Sorcerer 9) CR 10
Drider (9HD Aberration, Cleric/Sorc/Wiz 6) CR 7
Dark Naga (10HD Aberration, Sorcerer 7) CR 8
Guardian Naga (12HD Aberration, Sorcerer 9) CR 10
Spirit Naga (10 HD Aberration, Sorcerer 7) CR 9
Nymph (8HD Fey, Druid 7) CR 7
Lillend (7HD Outsider, Bard 7) CR 7
Rakshasa (10HD Outsider, Sorcerer 7) CR 10
Aranea (5HD Magical Beast, Sorcerer 5) CR 4
Lamia Matriarch (12HD Monstrous Humanoid, Sorcerer 6) CR 8**
Neh-Thalggu (10HD Aberration, Sorcerer 7) CR 8
Faerie Dragon (3HD Dragon, Sorcerer 3) CR 2
Garuda (11HD Outsider, Sorcerer 7) CR 9
Kirin (9HD Magical Beast, Sorcerer 6) CR 7
Lunar Naga (8HD Aberration, Sorcerer 5) CR 6
Royal Naga (14HD Aberration, Sorcerer 9) CR 11
Water Naga (8HD Aberration, Sorcerer 7) CR 7
Dandasuka (6HD Outsider, Sorcerer 2) CR 5
Maharaja (20HD Outsider, Sorcerer 18) CR 20
Marai (9HD Outsider, Sorcerer 5) CR 8
Tataka (18HD Outsider, Sorcerer 12) CR 15
After looking at the options out there, I think you are making the CR too high.
I think a good option for you would be use the Lamia Matriarch. It can already shapechange (have one crone form and one monster form), use spells (swap out sorcerer 6 for Witch 6), and is a monstrous humanoid. It is listed at CR 8 and 12 HD in the Bestiary 2.
i completely forgot about naga's having effective sorcerer levels. i was mostly using the raksasha as a baseline because i thought the overall abilities where gonna be close to what i was wanting. i plan on keeping the hd at 9 and then i wanna add more levels of witch to bring the cr to around 12. so if i add 4 or 5 levels of witch i think that might get me there. at first i was more worried about under rating its cr. but i definately dont want to put it to high.