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Since Moses has been negated, and his on-going prevent preventing PoZ’s triggered ability from activating has stop functioning then PoZ’s ability reactivates and can be used once the trigger condition is met.
But it didn't activate to begin with because it was prevented?
Another example would be Fire FoxesCrown of ThornsColiseumI play fire foxes into battle from hand, crown discards fire foxes, then I play Woes on my own Coliseum in that order.. Souls are protected.. an ability which isn't in play and which was prevented can somehow now activate as ongoing as if it wasn't prevented when played?
Maybe I'm beginning to side with Kevin on cascade negate..
Problem 4 would be all the cards who have "discard/banish to (some ongoing ability)."i.e. Uzzah blocks and uses his ability. He's now discarded and not in play, but LS are still protected from rescue. Your proposal effectively makes him not work.
It seems more intuitive, if you want to change the rule, to simply have prevented abilities be just that .. Prevented when played or not. Technically under the current ruling prevented mandatory ongoing abilities aren't actually prevented, they are deferred to phase completion.