Space Cyborg

Spacesuits can be so cumbersome, what with all that donning and doffing and trying not to die of explosive decompression, so why not cut out the middleman and just turn astronauts into cyborgs designed to survive in space as is?

I can think of a couple of reasons, but two come to the top of my list:

1. It might be hard to find volunteers to be turned into proto-Cybermen
2. Those you do find will probably the last ones you'd want to use–or be left alone in a room with.