I need some ideas / tips on things that can be done aboard for storage -
both for people who just 'week-end' and for the cruisers.

for food storage, dried food (fruit, veggies, oysters/clams/fish/shrimp/meat)
stores in a fraction of the space as fresh (and costs less to boot).

Also, vacuum packing reduces space needs for food and things like
blankets/clothing/etc.

For fresh drinking water, 2-liter soda bottles filled with tap water can be
stored in all kinds of out of the way spaces.