It would be nice to be able to do explicit joins on unrelated classes with HQL:
(hope this renders correctly)
select empl, phone
from org.example.Employee empl
left outer join org.example.PhoneBook phone
on phone.lastName = empl.lastName
and phone.firstName = empl.firstName
where empl.salaryGrade > 10
Note that this would also implicity solve because you could list join criteria that match what Hibernate would have chosen anyway (i.e., list a many-to-one relationship as a criteria explicitly).
Syntactically this could be disambiguated from the existing join syntax because the token after "join" is a class name rather than a property name.