Hmmmm... perhaps I have mis-labelled this.
The idea is not to cram a lot of HPA into something the size of a 12g. The idea is to build a very small HPA tank that contains roughly the same amount of energy as a co2 12 gram.
An 8/3000 is about the size of a soda can, so a 4/3000 would be about the same length, but would have a smaller OD. It's something that would have an ASA and pin valve, just like a 8/3000, 68/3000, 90/4500 or any other HPA tank.
As for the hazard to an Elephant... If something the size of a 12g filled with 4CI of 4500 psi nitrogen was really as dangerous as you stated, we would use them to hunt deer and wild bore, and leave the 3 1/2" magnum 12ga slug rounds at home - same kill, less noise. I could hunt in town
It's kinda funny - back in 1992 I was at a field and said "Y'know, we should drop this stupid co2, and start using nitrogen to power our guns. It's much more stable and is not effected by temperature change." the response - "Are you nuts! Whose gonna play paintball with a 3000 psi tank on their gun?" (of course people were already using it, but at this field in rural MI, no one had ever heard of such a thing). Around 1994 I looked over at my buddy and said "What I should do is use a micro-switch and a solenoid instead of that mechanical seer." the reply - "That's stupid! How much faster do you need to shoot?" (At the time I was using a Stingray...). Recently, I wanted to build a gun - a spool valve fully-mechanical gun using a pneumatic valve/switch for the trigger... I think GOG (and Yoda) beat me to it. Maybe I'm WAY off on this... But maybe there is some whacko thinking "that would make my old pump more accurate because of increased consistency regardless of ambient temp, AND I could refill it myself.... Hmmmm...."
I doubt I'm gonna see the day when guys are using 4/3000 or 2/4500 tanks, but it would be hellaciously cool to put one on the back of my old Nelson(s)