This kind of complex  , diverse, and distributed  enterprise application requires very very carefull consideration in terms of architecture
and requirement. If a specific part to be considered for ORM tool and move on gradually by taking one by one small application and
treating those as extension to the main application (using Hibernate), so here requirement of careful design  like TemplateDesign Pattern can
be a option  to give a thought. Database normalization is very important for OR mapping.