Is it possible for Alfresco to have a content property that will look-up other library/space document's metadata (like the one in SharePoint). Basically the values of this property should reflect the documents' metadata which have been look-up.
Yes, it is possible to do this. What you are asking for is a "dynamic constraint". You will need to write a custom constraint using Java to implement the lookup. Here is a post on the topic but there are several others.