I think this is a great idea but I don't think it should cost diamonds. Maybe Gold or Iron? Something more affordable. Also, I like the idea of not being able to send a lot but I think people could take advantage of the long distance. For example, your teammate is at someone's egg but they have Obsidian and your teammate doesn't have a diamond pick, he asks for resources, buys a pick and breaks the egg. People could rush way more easily so I think you should only be able to send it short distances. But I definitely think this is a great idea.