Hey wait a minute, doesn't your idea also have this issue? Say currently my name is Al Funky Stuff and I have a child with Lea Johnson Smith, the kid's surnames would be Funky (my patrilineal name) and Smith (my wife's matrilineal name). But my wife's matrilineal name is not actually matrilineal, it's her mom's patrilineal name. So we'd have to go and switch it out for her mom's second surname, which itself is her grandma's patrilineal surname, and so on. So you'd end up having to trace your genealogy regardless of how many surnames a child inherits. Unless I misunderstood your system?