Yes, it makes a lot of sense. I even think that Gradle folks are thinking about stuff like that. I can't point you to a online discussion about this, but I recall a conversation with Hans where he talked about being able to import project subsets and Gradle would choose if a project dependency should be 'jar-ified' to treat it more like external dependency in such a case.
So, yes, that does make sense. It does however not seem like something that would be easy/possible to implement on the tooling side. It will need some way for the tooling to specifiy the subset of projects they are 'interested in importing' and then it would be up to grade to ensure jars are built for the other projects.
The tools by themselves don't really have a way of finding or creating the 'substitute' jar.
This kind of feature would require tools and Gradle to 'cooperate'. Tools need to tell Gradle what projects they want to see as projects in the workspace... and Gradle needs to do the work to create the jars for the others.