I wouldn't say stupid idea at all. I would say that some people have had issues with pullet eggs not having great success rates for various reasons. It might be better to wait until the birds are older just so the eggs are full size, have good, thick shells, etc. That said, I've read plenty of stories where people hatch out pullet eggs successfully, so that would be a judgment call. After all, you would be the one seeing the eggs and knowing their quality. I would disclose to the other person though that they're pullet eggs, that way they don't think you tried to dupe them or anything if the hatch rate is low.
I can't speak to the crossbeak thing because I don't have birds old enough to breed or any with crossbeak. I think generally, though, people try to avoid breeding from any birds that have issues like that. But again, you're there with your birds, and you know the limitations, if any that the crossbeak is putting on the affected bird. I would say again that full disclosure about any issues like that would be fair to the person you're trading eggs with.