Hello.
Assuming a shaman already has picked the shaman hex: (witch hex) Choose any one witch hex for which you qualify.
If at a later level the shaman would take the Ritual hex feat:
Prerequisite(s): Knowledge (arcana) 4 ranks, Knowledge (history) 4 ranks, hex class feature.
Benefit(s): You learn to perform a special occult ritual known as Beseeching the Patron, which temporarily grants you a hex you don’t already know how to use. You always believe that your ritual is a success, so the GM should roll the required skill checks in secret, revealing the result only when you try to use your newly acquired hex.
Could the ritual hex still pick up another witch hex for which they qualify?
Oooh, that's a juicy one. Hmmmm...
On one hand, the Shaman can only select the Witch Hex once via its normal class abilities. On the other hand, you are Beseeching A Patron that is not normally a part of the Shaman's class features.
You'll have to reference the actual text of the RITUAL SPELL that you cast to make the final determination, specifically:
The caster gains access to one additional hex for which she qualifies. This ritual can be used to acquire a major hex (increasing the DCs of the ritual’s skill checks by 10) or grand hex (increasing the DCs by 20) if desired. The caster can have only one additional hex from this ritual at a time.
Unfortunately, I'd have to lean on the side of "No, you cannot select another witch hex as you've already got the one you could normally qualify for." At least, if I am going strictly off of RAW. If we are going off of flavor alone, I'd say go right for it as you are actually calling out to a patron to grant the ability to you.
If you want to play a shaman that can get more than one witch hex, try the Unsworn Shaman
I am highly inclined to agree with DeathlessOne, but then I came across the True Silvered Throne archetype.
Ritual Hex is given as a bonus feat in the True Silvered Throne archetype, and the archetype makes no specific rules/exemptions that modifies or disallows being able to select Major/Grand Hexes from Witch Hexes while using the feat. Since Shaman don't have major/grand hexes, this leads me to believe that they indeed CAN select major/grand hexes, as well as normal hexes, from the witch hex list; and it leads me to believe this is meant to be a feature of the archetype.
I would also say that this would be a feature when selecting the Ritual Hex feat normally, even without taking this archetype as well.
Witch Hex: The shaman selects any one hex normally available through the witch’s hex class feature. She treats her shaman level as her witch level when determining the powers and abilities of the hex. She uses her Wisdom modifier in place of her Intelligence modifier for the hex. She cannot select major hexes or grand hexes using this ability. The shaman cannot select a witch hex that has the same name as a shaman hex.
Shamans are only disallowed from selecting major/grand hexes while using the Witch Hex ability.
Tbh, I could see this going either way. My advice: ask your GM.
Could the ritual hex still pick up another witch hex for which they qualify?
You don't qualify for witch hexes, ever. You can take one via the Shaman hex called "Witch Hex", but "A shaman cannot select a hex more than once unless noted otherwise." Which means that once you have taken Witch Hex, you don't qualify for another copy, and thus can't select it with the ritual.
Thanks for the feedback.
Luckily, the GM allows it to work.