You can pick any claimant, or any dynasty member you make an elector.
Also, if passed, the succession type will be locked to feudal elective as long as 'full council authority' stands. Note that 'council authority' is available only for feudal kingdoms and empires.Only available to Muslims, Indians, and most unreformed pagans if 'full council authority' council law is passed.The same goes for eligible unreformed pagans, except religions which can use Eldership succession. Particularly for Indians, feudal elective is the only non-gavelkind succession law available to them with no technology requirements. One of the few succession laws with no tech requirements.