using established mechanics to supplement a novel idea is one thing, rehashing the core concept such as "give mono-death a mono-death repeatable death trigger" is unnecessary, it has been covered several times over, and im sure zanz has seen, considered, and rejected the idea many times over.
the other crux of the issue- consider how many death trigger cards death has, they are useable and balanced now. now imagine if the cat were made mono-death, they are no longer balanced. i dont care if it now "delays" and/or "brings it back to its original state" (which could just as easily be a buff against poisons and antimatters etc and/or irrelevant) another creature, all of those vultures growing one or more additional times per turn, having soul catchers instantly repay the cost of using the ability and then some. bonewalls growing, graveyards spawning another skelly for another alter (or could multiple alters delay the same creature over and over in the same turn? even worse) etc etc etc. if there is to be a mono-death repeatable death trigger card, it would have to have some substantial novel balancing mechanism beyond just that of a delay, or anything of the sort.
edit- easiest example to find of a similar card is necronomicon in level 3, which flat out sacrifices a creature, a bit more harsh than just delaying it and/or 'refreshing' it.