You are not transplanting a whole body, you are transplanting a head. If this paper is to be believed, there is a smaller risk of a hyperallergenic reaction for some reason. IANAD, but maybe it's because the head has no organs in the sense that it doesn't contribute to the production/purification of blood.

There's all kinds of afflictions that might threaten your life but not your head, from cancer that's spread to a critical organ to blunt trauma to any critical trauma. If something destroys your body, this might be the last and only solution.

The children will be biologically of the new body you have. I don't think anyone has written a law on this yet, but I suppose the children will be legally yours, and yours to raise and culture :)

Most of our identities is in our heads, though some things linked to your character are linked with things in your body. Perhaps your appetite is, and perhaps your preference for sporting/outdoor/indoor activities. I bet a lot of this is not yet well known or researched, and the world would be very intrigued by how you feel about things after the surgery!

I can imagine people that are paralyzed from the neck would want to participate in such an operation. "Donors" would be people that have are brain-dead with intact bodies. However, current organ donor rules probably do not regulate the donation of your body as a whole ... That said, such an operation probably will not play a big role in the future treating such crippling injuries.

Maybe it is extremely difficult, but it's also fairly common regardless. Transplants are being done every day. If someone cannot be fixed in any other way - that's often a "cheating" way out.