On Sun, 4 Feb 2018 02:03:00 +0000
(Roger Hayter) wrote:

And the floor is not strong. I am concerned
that a sufficiently rigid cage not to flex by the few millimetres that
would cause a leak would be inordinately heavy.

An all-around curtain is very light and could flex without leaking as
long as it stayed inside a deep shower tray. Then you just have to
support the plumbing. ISTR seeing somewhere a "telescopic" curtain, a
cylinder of fabric supported on hoops that hung on a pulley system.