There are two questions here: (a) what's the actual value of this idea, and (b) what's the right thing to say to a child who has come up with an idea like this,

There are two questions here: (a) what's the actual value of this idea, and (b) what's the right thing to say to a child who has come up with an idea like this, in order to give them the correct amount of encouragement without over-praising them? As the cold-hearted over-educated curmudgeons of the internet, we're allowed to answer part (s) without worrying about part (b). The kid's dad has to worry about part (b) for himself, but I hope the kid's dad has enough perspective to realize the correct answer to part (a) is that it's worthless.