Replying to myself because it seems as good a place as any...
We could walk the tree of a module and patch up any symbols we find that were referenced in a def or mac, but that's not a clean solution, since it can't find all actual calls (something could be building up names, for example, which we'd never find by walking the tree).
What this means is that any module system built right now, as far as I can tell, will have to require support from those writing the modules, but since renaming modules is implicit in how import.arc works at the moment, there's no way to know what the call should look like, for the module programmer. I can't see any way around this except to change Arc itself to make function and macro definitions respect lexical boundaries, rather than all being bound at the top level. Until that change is made, all we can do is fake a module system.
