I work with Neil on the Oracle team, as Product manager I feel perhaps locking is still a confusing feature of the tool.
Our aim with locking was to provide teams working on shared development schemas a means by which to 1) avoid clobbering each others' changes accidentally and 2) communicate what they were working on to one another.
The use case you describe is something we see less, but that we understand would be valuable to some teams working on separate, sand-boxed, development schemas. We currently see a better long-term solution to that problem to be to offer a "merge" to the second person, but in the meantime we currently offer a "take mine" or "take theirs" to resolve the conflict. There is nothing stopping you at that point going to either the database or the file system and merge the object yourself.
Hopefully that helps?