Two thoughts,
In many parts of the world, red traffic lights now have timers that tell people how long until it turns green. It seems that this information reduces stress and prevents trouble. Rough information of how long and why the light is on would seem to have a similar positive effect on passengers.
Second, any room for a three position seatbelt light on the next generation of planes?
1) Red - Everybody bolted down (SLF and CC)
2) Orange - Essential out of seat only (no more than quite light turbulence only??)
3) Yellow - Stretching your legs at the doors and waiting in loo lines fine
TME