Other: 3 turns cooldown [already suggested, likely]. 1st turn you're under sosac, lose 40/48 HP and regain as much as the opponent hits you. 2nd turn, you're under sosac, the enemy heals you, then you exit the Sacrifice condition. 3rd turn, survive by other means [Sundial, more health than enemyatk+40/48]; 4th turn, enter Sacrifice again by playing another sosac. This would make Pulverizer, Explosion and bolt spells pretty dangerous [you have to play multiple Sundials and care more about bolts], and Unstable Gas/Catapult would become even more powerful against sosac [you can currently chain sosac to prevent being damaged by these]. In addition, it would give you 1 turn to crush arena decks with 12 Shards of Sacrifice; also, as of now you can play 2-3 Shards to prevent being silenced to death.
A cooldown to sosac chaining would ultimately give way more power to its current counters.