Don't underestimate perennials in making your gardening life easier. Perennials will continue to come back every year and will only require minimal maintenance such as weeding and fertilizing. You'll save time by not having to plant and care for seedlings
Gabion walls don't need any kind of drains because they are porous throughout. Gabions can be customized to make them more useful in public spaces. Gabions can be filled with any heavy material--diverse stones, metal artifacts, obtanium, etc.