I'd like to see a counter to units that can return aswell. Maybe in this suggestion or another form, i don't know... It might also be better to just go the oldfasion route for them and directly balance(aka. nerf) these units.
A counter to only 2~3 units can quickly become 'to specific' to be viable (although the card can serve other purposes aswell to make up for it, like also "stopping" Grims) and it may not be possible/to difficult to script. But that's a problem we don't have to concern ourselves with. (I can see it work by simply blocking cards from getting back into the cardfile, but this may give trouble with other "return to cardfile effects" like PriestOfMadness and SS's...)