Isn't scaffold more effective than capsule ? Same mass but 7 times the HP.
Asteroid rock capsules have 50hp and 0.01 mass while scaffold have 75 hp for 0.01 mass.
So they have 1.5 times more hp.
Advanced armor without effects have 1400 hp((250 + 100 armor hp)*4 due to reduction) and weight 0.25
So without mods capsules have for 1250 per 0.25 advanced have 1400 per 0.25 mass and scaffold have 1875 per 0.25 mass.
Scaffold without mods is the best per mass advanced is the best per mass with mods(as long as it is not facing punch through or other similar weapon mods).
And capsule is the best per $ and is not much less efficient than advanced armor without mods.
So the lesson is : use advanced armor only if you use mods or want high density without stacking and never ever use any armor under advanced.
Use capsules if you want to have ships with armor and do want to economize money and use scaffold if your ultimate priority is health per mass and that you do not want to use defensive mods.
Scaffold is indeed a good block if you can spare the money.(not as good as advanced armor with mods but it is not always convenient to put mods on a small ship)
the reason why using basic or standard armor is a bad idea is the following:
Standard armor have 729.17 hp(counting the added armor) per 0.25 mass while basic armor have 625 hp per 0.25 mass
if you plan to take the first hits with advanced armor and use those low level armor to store armor it is still a bad idea: hull now gives your ship 1375 hp per 0.25 mass but it is less efficient in practice due to how armor sometimes works(breaking a block with stuff like punch through allows to cause extremely high damage to armor compared to the hp of the block) and heavy armor gives less than basic in this use case.
Now the thing is that I through about using capsules as structure hp storage: make a whole lot of spaghetti of capsules spreading on gigantic areas for distracting shots and having structure hp that takes many hits to break.(since you can only break some blocks at each shot and that there is a whole lot of them spread)
You can make a drone with absurd volume since volume is not what costs in a construction so why not make spaghetti drone that are cheap and thanks to huge volume can have good powergen(since now it does not cost much generators it costs more space and space is free) and thus good weapon systems.