At UW Oshkosh we created lots of "workflow sites" that used PloneFormGen and uwosh.pfg.d2c to create forms that, when submitted, generated Archetypes content items containing the form values, to which you could apply a custom workflow (also see plone.app.workflowmanager). You could add custom indexes that let you search for values in any of the fields, and you could create collections based on those indexes.
That would still work with Plone 5 despite P5 being Dexterity if you installed Archetypes (still works). Or you could do something equivalent with collective.easyform and there is an easyform -> Dexterity content mapping add on I forget the name of at the moment.