Here's a thought for flexibility but not all-powerful ship's locker-
Use the 68A system, and determine the role of the ship locker, specialized or general-
SURVIVAL- space survival including vacc suits, extra life support, etc. and ground survival, tents/shelter, environmental clothing, general medkits, extra food/water, comms, hunting/tools, etc.
SHIP DAMAGE-heavy engineer rad suits, extra ship tool kits, common parts, cabling both power and control, spare plating/sealing, medkits for large scale hits/rad damage, emergency life support/power, etc.
COMBAT- small arms locker with matching ammo, at least 1-2 heavy support weapons/missiles, personal armor, medkits for wound trauma, non-lethals for passenger control/security, 1+ boarding suits and hullcutters/demolitions, grenades/mines, etc.
EXPLORATION- as survival but geared towards either space or ground exploration/prospecting, with more sensors, sample gathering, analysis tools, etc.
MEDICAL/RESCUE- as survival but past vacc/enviornment suits, cutting gear for access to wrecks, full paramedic/trauma medkits, pharmaceutical suite, full surgical tools and equipment, infection conrol, etc.
MERCHANT- a mix of space survival, tools, non-lethal security, and merchant small trade items, plus the ship's safe.
GENERAL- a smattering of all of the above.
General rules of thumb-
- Start with 6+ as basic roll for item that should be in it's specialty locker.
- Add two levels, to A+, if it's an item that would NOT be in that specific specialty locker.
- Add one level, to 8+, if rolling against a GENERAL locker.
- If an item is rare and expensive, add 1-2 levels.
- If an item is available, the next time it's rolled for increase the level by one.
- If salvaging/looting a wreck/piracy, add 1 level.
- If the level increases past the A+ roll, it's not available.
If an item is not there, it can't be rolled for again, it will have to be restocked. Or if you like the whole maker concept, then you CAN reroll to have a maker make the item, but if the roll fails again there are not enough of the 'right' feedstocks to make an emergency version of the item. Emergency maker versions are not production quality control and have to be checked for avoiding breaking 4+ every time its used.
I'd say the ship's locker is part of the bridge cost and tonnage, and is 1dton of that bridge per 30 crew/passengers. The cost of initial equipping is covered in the bridge cost, probably half of the per dton cost and the rest is special protection/armor/security doors/locks- this is after all the last line of life of the ship in this room.
If additional specialized ship's lockers are desired, just use the 30 people per dton and bridge costs for your version. That would allow for better survival chances and a die roll per locker, lessening the risk of being caught short.