Threshold activated planeswalkers with conditions particular to the planeswalker. Like Ascend, but dependent on the planeswalker in question.
For example, Saheeli Rai cares about artifacts. Say you can't play her before you control three artifacts. Other solutions could be to inflict a set amount of damage one turn for Tibalt, or controlling a set amount of elves as Nissa (yes I know that Nissa has since moved away from caring about elves - it's just to demonstrate). Having a number of cards in hand as Tamiyo or having several zombies in your graveyard as Liliana.
This means that most decks will have a potential planeswalker available to them, but it means that a generic azorious deck (ideally) shouldn't saturate itself with two teferis and six other walkers.
The condition may seem limiting as it requires a board state and timing. But here's another idea that they may have implemented. Perhaps you can play the planeswalker any time, but it can't lose loyalty or activate any abilities before it actually reaches its condition.
I played Quests back in Zendikar and they worked great. There is a real problem about requiring text for the above, however, without exploding in complexity.
For example, Saheeli Rai cares about artifacts. Say you can't play her before you control three artifacts. Other solutions could be to inflict a set amount of damage one turn for Tibalt, or controlling a set amount of elves as Nissa (yes I know that Nissa has since moved away from caring about elves - it's just to demonstrate). Having a number of cards in hand as Tamiyo or having several zombies in your graveyard as Liliana.
This means that most decks will have a potential planeswalker available to them, but it means that a generic azorious deck (ideally) shouldn't saturate itself with two teferis and six other walkers.
The condition may seem limiting as it requires a board state and timing. But here's another idea that they may have implemented. Perhaps you can play the planeswalker any time, but it can't lose loyalty or activate any abilities before it actually reaches its condition.
I played Quests back in Zendikar and they worked great. There is a real problem about requiring text for the above, however, without exploding in complexity.