Depending on how defined a track you want to be following, the Hume and Hovell walking track comes to mind. There's some info -http://www.takeawalk.com.au/HumeandHovell.htm. It's not really a remote wilderness walk, but enjoyable and due to it's length and many campsites, a section can be chosen to suit your requirements.
Another walk could be the Mittagong to Katoomba walk. Some sections can be a little hard to follow in places, but it's generally good and if you can use a map and compass you shouldn't run into any issues. My recommendation would be to start at Hilltop near where the starlights trail starts, and finish at either Dunphys carpark or Katoomba itself. It's probably only a 7 day walk, as some have dones it in a quicker time, but there's no reason why you couldn't spend a day exploring at the Kowmung or Kanangra, or you could even make a detour up onto the Blue Breaks. Some information can be found on this forum here -
http://www.bushwalk.com/forum/viewtopic ... ba#p129094 or here
http://www.bushwalk.com/forum/viewtopic ... mba#p96366Also check out this topic for suggestions -
http://www.bushwalk.com/forum/viewtopic ... ba#p137619