Deleting clips shouldn't remove their instance from the timeline
You should have the option of not removing clips from a timeline when you delete them from the project. In FCP7 you could simply have a single timeline, without referencing specific imported clips.
Also, it would be great to click on a timeline and have Premiere generate the clips that are missing.
I agree with Micah, it should not delete while remaining in the sequence. I would however like a dumby or offline clip in the sequence if I delete its source. So I could find the deleted clip again if I needed to.
Micah Haun commented
Nope. I don't miss FCPs phantom sequence clips with no master clip.
Premiere has a lot of work that needs to be done with managing master clips in the bins, especially merging duplicates, but there is no reason whatsoever to delete a master clip without fully removing it from the project.