Create a custom kit that allowed for emergency supplies.

Have a set of items that are permitted to be added to the custom kit (eg: things already in existing kits)
Have a set of items that are not permitted to be added in the custom kit (eg: rare or valuable items)
Each user with the feature would have 1 custom kit, more could be added with Custom Kit+.

Some balancing ideas:
Have a cooldown of 1 day, and every item has a weight value where you can not exceed a certain weight in the kit.
-OR-
Have a cooldown that is calculated by a system where every permitted item has a wait value in seconds that, when added together, equals the cooldown time.

And if a user has any other kit features, they should be able to add them to the custom kit, but with those items costing extra weight/wait points. But if they don't have, for example, /kit water, then they can't add sponge to their custom kit.

Examples:
Emergency rations kit: 10 cooked porkchops
Emergency defense kit: 1 sword, 1 sheild
In a Pit kit: 128 gravel