What are your thoughts on a sitdown shower
A sitdown shower with toilet (composting or otherwise) is called a "wet bath". Searching that term might give you some ideas.
Showers are relatively rare in nomadic contexts because they require relatively large amounts of water, even "navy showers".
Sponge baths (washrag and basin) or baby wipes are quite common.
many rv's come with those type of showers these days.
ah..but there is a new thing..
a high pressure hand held shower head that used minimal amounts of water..
like...a couple of pints..
I removed the faucets from my thrift store sink and installed only a dish sprayer with 6' hose. It reaches outside the van's sliding door so I can wash up or rinse things outside. The 12v water pump (already installed) provides pressure.
Dunno about high pressure but it works for a navy shower.