for VIA I recall the ensuite toilet and shower being good, but you had to think ahead as after you used the shower the toilet seat was covered in water! Pic here
https://www.seat61.com/montreal-to-halifax-by-train.htm
or
https://www.seat61.com/images/nightjet-toilet-comfortline-large.jpg
Another pic of the same bathroom
https://www.seat61.com/images/nightjet-deluxe-top2-large.jpg
Those pics show how it should be done;
the bathroom is a factory-built sealed pod, that then slots in (how it's now done for hotels & student accommodation)
the shower area is lower & so the water can't go anywhere else
I think that upgrading seated passengers to berths is fairly standard practice when the seated coach is faulty, assuming there are any spare berths. Tuesday night in any direction on the Highlander is likely to be comparatively quiet at any time of year. Just under two years ago, I did Euston to Inverness on a Tuesday night in late August and both first and standard class were no more than a third full. In my experience, Tuesday is probably the most likely night of the week for there to be enough spare capacity for displaced seated passengers/walk-ups. We’re probably not yet in the absolute height of the season yet either, particularly as school holidays haven’t started in either Scotland or England. July and August are the busiest months for the Highlander, I think. I wouldn’t bank on there being any spare capacity on a Thursday or Friday night northbound or a Sunday or Monday night southbound at this time of year though, that’s for sure.