Don't forget the other stuff, like latch valves, filling ports, and the percentage of the volume not available due to the membrane many tanks use to isolate the pressurized gas (often nitrogen or helium) from the liquid. There's also likely issues with efficiently putting all of those small tanks inside of a structure.

I wonder if you probably could make a fiber-wound composite tank for hypergolics. It's be tough to do due to the corrosive effects of the liquids. I wonder if it'd be practical to make a thin-walled stainless steel tank and then spiral wrap it with carbon fiber for extra strength. An all stainless steel tank designed for 300 PSI would have to have fairly thick walls. Going to even higher pressures make the problem even harder. Carbon fiber might make the tanks lighter by letting you get away with thinner metal walls. Another possibility might be all composite tanks with a ceramic lining to prevent corrosion.