Is the pump out an easy fix?
I see places are now charging £20 to pump out.
personally, I use a cassette toilet and it keep things simple,
there are plenty of places to empty a cassette, and at no extra cost.
If and that’s a big IF, I had a private mooring with a bit of land I’d go for the composting method and use the compost on the land.
but as it is, with being on the move all the time a cassette is so much easier.
save time, effort and stress,
go boating instead 👍