I really like the idea of the flipwalkers from Magic Origins and M19, and think it's a very good way to represent sparking. So, I decided to do a few more
When Ajani, Nacatl Outcast enters the battlefield, create a 2/2 white Cat Warrior creature token
At the beginning of your postcombat main phase, if a creature you controlled died this turn, exile Ajani, Nacatl Outcast and return it to the battlefield transformed
+2: Gain 5 life
-3: create a 2/2 Cat Warrior creature token named Ajani's Pridemate with "Whenever you gain life, put a +1/+1 counter on this"
-11: You get an emblem with "Creatures you control are indestructible and have lifelink". Then, if you have 40 or more life, create an emblem with "Whenever you gain life, put a loyalty counter on each planeswalker you control"