What I did for javascript was to by default, have no ordering. Optionally you could specify an ordering.
It would make sense for a package to use some sort of key ie:
package_key_${order} when doing the ordering.
This is how I got the richtext javascript to load in the correct order.
So for Zen CSS
we could have Zen_1 Zen_2 etc. and the zen theme would specify the loading order.
