If this is available somewhere else please tell me to save me the work.
Sources I'll be using/referencing to are listed below, so it should already be enough for most people, but I'll make this easier in a few days when I am sure no one has posted this already somewhere else:
http://www.bitvise.com/winsshd-for-sftp
http://www.superflexible.com/partial.htm
Later I'll add:
http://www.superflexible.com/mangling.htm
http://www.superflexible.com/restore.htm
I won't be covering certificates at all, although it could be useful. But I don't feel like the right person to explain other users about this kind of feature

I'll probably finish this in 2-3 days