It seems a little weird. I don't quite get it. During your turn, you play it; then your opponent sets aside a card; then during their turn, they discard it and only draw 4 cards. OK, I get it now. Discard down to 4 this turn, pre-minion for the next turn.
I think it could work. The interaction with moat is clear - if you have Moat in hand when it's played, the attack gets moated, but by the next cleanup phase it's clear there's nothing that's left to moat, the attack is playing out. It might end up too confusing for actual play, not sure.