For example a political post in s/nopoliticshere can be moved to s/politics by the mod of s/nopoliticshere.
This accomplishes several crucial things:
1) Prevents censorship (and drama) by not removing the content. The same thread exists, just in a different sub and still shows in s/all.
2) Grows niche subs. Maybe nobody goes to s/politicalmemes but they will if they like the content that gets moved there from s/funny.
3) Keeps content relevant to the sub in two ways - subs get relevant content imported from other subs, irrelevant content gets removed from the other sub.
Discussing this in IRC the main concern was abuse. A mod can dump a bunch of posts into other subs. A potential safeguard would be for mods to disallow transferred content from other subs. When another mod tries to transfer content there they get an error and have to choose a different sub. And of course the receiving sub can just transfer the thread again if they wish if they allow transferred content.
There still has to be a full deletion option for illegal content, but I think those instances are few and can be handled through an admin reporting system.
Should have something on the post saying where it came from. The submitter should get mail saying where the post went as well.