You might want to check out Rex Hash plugin:
It allows you to create hierarchical ("multidimensional") dictionaries. This way, you could get a better structure of your stored data, creating objects like this:
world1.title = "Cool World"
world1.enemies.0.name = "Evil bunny"
world1.enemies.0.health = 100
world1.enemies.1.name = "Nasty kitten"
world1.enemies.1.health = 150
world2.title = "Warm World"
...and so on.
All with just one object.
Maybe not the best example, but I think you get the point.
Although Rex plugin is great, it lacks some features like sorting on keys or values, so you might need to complement it with normal arrays. My own plan is to modify the plugin, or create my own, to support sorting once I get there, as I feel that arrays are too limited for most of my needs.
Unless you're updating huge amounts of data at the same time, performance shouldn't be an issue.