Access z3c.form raw value from url?

Is it possible to access the raw value of a field by an url?
Something like http://localhost:8080/Plone/mydocument/text/raw
I had the impression there something like z3c.form field traversal with ++widget++?

Background is that after migrating a site to Plone 5, some pages are producing an error when editing

As an easy workaround I'd just copy the raw data, correct it as needed manually and create a new document.

Wild, wild guess:

Could you make a view

<tal:define fieldname='context/request/fieldname' 
     tal:replace='structure context/?fieldname/value />

And then http://path/to/content/?fieldname='my_field'

With a bit of help (thanx @datakurre) I manage to find it.

For the example of the rich text field, you can access the field value with http://localhost:8080/Plone/mydocument/@@view/++widget++IRichText.text

There are also at least a render property which seems to render the just the value and a value property which is not publishable, but should be accessible from TAL, but can vary depending on which field/widget combination you use.