I think Doctor Manhattan, in some ways, represents nuclear weaponry. A new thing in the world, with more power than we really know what to do with.
I've always wondered why Jon chose to make his body so un-human - surely he could have done it differently if he wished? Maybe just a literary device.
In some ways, yes. In other ways, no. They definitely talk about having Dr. Manhattan the same way we talked about having "The Bomb" prior to 1949. However, there's no "balance of power" involved in Dr. Manhattan to shape history from 1949 until 1986, and most of the World's history was shaped by that. With only one Dr. Manhattan, he means a lot more than nuclear weaponry. I don't think Dr. Manhattan chose to make his body un-human - after all, he spent months painstakingly reassembling it from the aether. I think he got "close enough" and stopped. Dr. Manhattan, after all, drifts further and further away from humanity. "Brilliant blue skin and no pupils in his eyes" is only foreshadowing.
In some ways quite explicitly! I think ... why would he make it human? He's not human anymore and doesn't attach any special significance to the word human. If anything I think the fact that his body is still recognizably that of man is a literary device that Moore needed to have him interacting with other people semi-normally.I've always wondered why Jon chose to make his body so un-human - surely he could have done it differently if he wished? Maybe just a literary device.