Why not suggest something sensible, cost effective and not so permanence ??
Portable tall room partitions/dividers. They'll be far less expensive then you painting or putting up vinyl. I've heard of some of those vinyls, actually causing the glass to crack or break, due to certain conditions.
Anyone ever try this?
3M™ Blockout Film 3635-20B White Matte 6 mil 48" x 50 yards
yep - stuff is true blockout - matte white face, black black black adhesive side
We have done this for many times for a particular tanning salon company. We just use a black high performance opaque vinyl on the outside. The we put large graphics for the salon over that.
This has been on the glass facing east since 2010.
Don't judge me for the graphics, customer had this long before I started.
He wants some sort of vinyl. I would be worried about putting black vinyl on the inside. I am pretty sure it makes the heat build up in the two pane windows and can shatter.