I am running El Capitan Beta, but this question would also apply to Yosemite. 

I want another account's (account B) "Photos" app to link to my primary account's (account A) Photos library **without** moving my library to an outside drive without permissions. I can't point the Library from the Photos App in account B to to the Library in account A. I have added Account B with full permission read and write with extended ACL permissions to account A's /User/AccountA/Pictures folder and Photos Library. Verified with ls -le.

So... the best solution I see is to create a hard link from /User/AccountB/Pictures/AccountBLibrary -> /User/AccountA/Pictures/AccountALibrary so that it always points to that inode. Can anyone see a reason NOT to do this or a better way to link the two **without** moving my photos library on Account A.

Edit: Well for one - you can't hard link a directory (which obviously pictures libraries are)... so to reword my question - What about soft link? (Symbolic) (Thanks fd0). And now I can see - It produces the same error (because it isn't a hard link). So... can I accomplish this?

The goal is to not duplicate photos (I use iCloud photo library, but I don't want to duplicate even "optimized" photos).