How come it's not possible to replace media with a sequence?

I cannot believe that it is not possible to replace media or make a sequence mimic a media file so I can replace the source of a clip edited with a sequence. I'm literally exporting a sequence right now just so I can replace media in the project window. I find that to be ridiculous.

Thanks for the replies however that's not what I'm asking

Let me explain,

I made a trailer out of an internal use only video so, low quality and watermarked. I, then, received the master video however a shot was cut out of it. Therefore I wasn't able to simply replace media and retain the cuts and timing in the trailer. So I figured ok I'll just put the master in a sequence and put space in place of the missing shot and use this sequence as the new source for the trailer sequence. That is not possible. I also couldn't replace clip from source monitor or bin because there's no option do that and preserving the timing at the same time it just replaces like a caveman. So I literally had to export the master seqeunce I manually synced to the old internal use only footage and replaced media with that. But that's silly.

Thank you