Yes, I wouldn't want the library to get cluttered up. But I, just the same, don't want my disk drives to get cluttered. I use MC essentially as an extension of my folder structure. If and only if a file exists do I want it in MC--and if it exists, I want it in MC.
Why not add the ability to, while playing a channel, go back in time with rewind and just jump back through any available time-shifting? Then it would be available without adding more entries.