In the Unix story we tried to use common shared libraries, common OS installations with a lot of services, to reduce space usage. But this method is non so flexible, infact now we use virtual machine, docker container that eats a lot of space but are so flexible. I don't think reduce disk space sharing the same file is a good idea.
It all depends on how many clients are people expected to use. I am expecting that people will use between 30-100 clients if Nostr wins. So, It will take a significant tow on disk space if all the information gets duplicated.