apt-mirror supports multiple architectures but normally searching for information about it just pulls up tons of pages advertising as much. I finally found an example here off which I based my configs.
Read it here
I talked about this a bit in an earlier post but wanted to talk about it a bit more as it comes to multiple architectures. We run vmware vms on debian hosts with gobs of memory so generally they're amd64/x64 but often the guests are i386/32bit debian installs to not have to deal with the ickyness of amd64 and compatibility like libraries.