I fully agree with keeping our country clean, the only thing I hate more on the bush than people leaving surface turds is rubbish. We are going to use scented garbage bags with baking soda stored in a large protein powder container for solid waste and empty water bottles in a drysack for liquid.
I just setup my 2:1 haul device today which can be seen here https://youtu.be/3GN066ctHgA
We thought about space hauling but we don't want the extra risk and complications associated with it while we already have a steep learning curve underway.
As for a belay seat, the wife's have already cracked the sads about the spending for this trip and more gear is out of the question. As it is we are building the seconds set of ladders out of old rope and sharing ascenders.