Interesting.
Yes, for a spell (whatever its name) with the requirement that the creature must be dead first to me means the spell would be a reasonable level 1 spell for balance purposes, since you must defeat the creature first.
Of course, it very well can't be allowed to prevent Resurrection or Wish in that case. And you might want to up the level somewhat just to put a lower limit on the business of soul harvesting.
But I don't see any huge problems with making such a spell level 4, say, provided the language about preventing resurrection is changed to require the spell to be cast at least at the same spell level as the restorative spell.
So for example, in 5th edition, the spell would indeed prevent Revivify from working. It would have to be cast using a 7th level slot in order to prevent Resurrection.
If we instead use Pathfinder 2, the spell must be heightened to spell level 5 in order to prevent the basic Resurrect ritual or the Breath of Life spell. It would need to be heightened all the way to level 10 to foil a Wish.