Re: Gas fire suppression is bad for hard disks...
One alternative I've seen elsewhere is a set of individual fire-extinguisher "tubes".
You put one inside every piece of kit the could start a fire.
If it starts heating too much the tube melts at the hottest spot and poof! the fire is doused.
There's a sensor at the end of each tube to detect a discharge.
It probably damages the kit it's inside - but that was on fire anyway.
Quiet, simple and relatively cheap.
Couple with a zoned sprinkler system over the AC and I suspect you'd never lose more than the box that went on fire.