The second most popular idea is probably a module system. I honestly don't know much about what that would entail, beyond reading rocketnia's comments in his ns.arc from 7 years(!) ago.
Basically, it seems kinda hard, because of how much arc currently depends on global tables to collect special objects like macros, the interactive help stuff, etc.
We could just decide that Arc is deliberately focused on 'hackability', like emacs, and that modules are unnecessarily refined and restrictive for our uses.
