Line the driveway on Johns side - Syzygium australe 'Aussie Southern' / Lilly Pilly. Could be good for screening the neighbour's garage, behind the jacaranda. Looks like it is quite narrow, or can be kept that way at least.
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.