I did a water conserving bathtub for a space station--one with artificial gravity(that is the space station has AG){although a tub with artificial gravity might be interesting}--anyway, the tub is shaped(roughly)like an average sized human--anyone above average has to stand and shower. Anyway, the point here is I recently looked at a brochure for the Safe-Step walk-in tub and it looks like they are half way there but much more generous toward those with a little girth.
As to the concept in the OP. Sounds half way to the typical colon flush--so: my thought is, 'why not go all the way and make it a sort of colon flush and bidet?'
Perhaps the more personal part should already be in the anus and the toilet has a quick connect for that. That would at least give an illusion of something more sanitary.
Then, of course that leads to that place where someone might say ,"I'd ask what's up yours; but I have a fair idea already."
You know; off in space in strange conditions a good colon flush might be what one needs.