Senjutsu
Senjutsu is only to be learned by one person of the village and only the village Kage can choose who is to learn it.
The Senjutsu that is taught in the sand village is still unspecified
Once that person gains Senjutsu only one person can be taught the senjutsu and only when the Senjutsu teacher dies can the student become a teacher and take on a student. Only two people at any time can have the Senjutsu, a teacher and a disciple.
Jinchuuriki/ Inner Demon
A monster locked within the user, this doesn't neseccarily mean it has to be a tailed beast but then again if a Tailed beast decides to stroll into the sand village then hey, I can't stop it from dying and being sealed.
Most of the time a monster will be sealed and can be anything from a sand beast to a huge summoning monster.
Only 3 people can have Inner creatures/ monsters at a time, this includes the current Kazekage.
Cursed mark
I haven't decided much in regards cursed seal but if any ninja should wish to choose to become a Cursed seal Clan of Shinobi I wouldn't mind considering it.