From your perspective this looks like a good idea. But i see a lot problems. First you cannot delete an object if a detail was created with it. Second, information from this object can be used in another pattern piece. What to do in these cases?
Your way of thinking very familiar to what i do when debugging code. But thing is not so simple with patterns. There are a lot connections. Right now i don't see an easy way to make "delete last".
I think to make this idea more mature you should think more. The basic idea is clear, but still did you think little bit how would you implement if it would you who code this feature?
I have doubts that deleting it is really what you need after all. But let's continue this discussion. For now it is not NO, it's rather i don't see it real.