stealing does not mean kill or destroy, its the transfer of ownership or control, so when a creature would be stolen, no death effects or end of the turn effects would be triggered.
antimatter is a good comparison to a card that steals a creature.
antimatter
-negates the damage the creature does totally
-heals the opponent
-if a 2nd same creature is in play, the player is no longer healed, but 2 creatures now deal effectively 0 damage, one negating the other
that is only one card, just one which can nullify the damage done by 2 creatures. so the idea of stealing a creature completely is not over powered at all, IT IS NOT CONSIDERED KILLING EITHER, and a stolen creature can be stolen back, just like an antimattered creature can be antimattered again.
if it works for other games, theres no reason why it wouldnt work here, we need new abilities and crap, and since a discard pile will never happen (even though that opens up a lot of new abilities and effects/spells), every other feasible ability/skill/spell has to be at least attempted, the card could be made and if it is too game breaking, it could be removed. it just needs a high cost like fractal, and the quanta drained, like fractal.