I also did a single delay card once. It was a cantrip trasher, costed $2 and was only gained a shuffle later. It originally said "When you gain this, put it aside, and put it in your discard pile after you shuffle.". It was both too strong and hard to remember. I increased the price to $4, and we were getting somewhere. Still to hard to remember and slightly strong, though. As it costed $4, I felt that I could just cost it at one Potion instead, make it trash that Potion and return the buy on buy, which is what I did. Except for having the Potion in your hand once, the outcome is pretty much the same. In the end, it didn't even return the buy. Take a look at "Homunculus" in my thread if you like.
Obviously this isn't a general solution, but I didn't find the mechanic interesting enough for more than one card, either way. Maybe a mat would have changed that. However, I think a card that sets aside others to miss the shuffle could just be a duration, tbh.