Please understand that I am writing about a personal experience with a ESS fire bottle. I can see merit to the concept of the system, but I also see issues.
I bought a used Rx7 some years ago for my Son to start racing in SCCA.
It had a ESS fire system on board and looked like it had been there for awhile so I decided to remove it and re charge it.
I unbolted it and went out to the driveway to release it. I pulled the cable and it let loose, spraying foam everywhere, even from under the cap affixed to the bottle and from a crack in the end cap. Upon cleaning up the bottle and opening it up to rinse it out I found the cap was a plastic piece, cracked and what appeared to be possibly cross threaded at one time (damaged threads).
After thinking about what I found, I decided to use a normal pressurized bottle with gauge and would deal with having to take it to be refilled/charged etc.
my $0.02, the agent was not completely discharged thru the lines because of the cap damage/failure. If this had been a pressurized bottle the gauge would have indicated so and leaked everywhere. Then I thought about the cartridge, there is no indicator on it, can I trust it?
I saw the pictures of a Gentleman who died in a race car. Plain as day, he pulled the handle of the cable trying to release the fire system only to have the safety pin still in the bottle about 6" out of his reach.
John