Hi John,
Nice try, but if you add the same field ("Additional Driver") to multiple forms ("Additional Driver 1", "Additional Driver 2"), Workfront will consider all of the "Additional Driver" fields to be the same and "point" them at the one-and-only parameter value in the database. Towhit: although you can add John via the Additional Driver 1 form, when you then add Doug via the Additional Driver 2 form, Doug will overwrite John.
Your first (yucky) approach is a common workaround (Additional Driver 1 = John, Additional Driver 2 = Doug, etc.) and those so inclined might soften the blow by adding form logic to "reveal" each Additional Driver section only when it applies (e.g. "Add Additional Driver 1" checkbox...click..tah dah...)
Another potentially more elegant (albeit frowned upon by purists) is to consider leveraging the natural one-to-many relationship that does exist and does allow custom data at the Issue level (or Task, or Project for that matter): Expenses. To risk this road less traveled, each Additional Driver would be a special Expense object under the Issue that captures Additional Driver, Additional Driver License, etc. resting assured that because each is its own separate row, Doug would never overwrite John.
I've taken the latter to extremes over the years, with highly satisfactory results (including charting...mind...blown...). Good luck!
Regards,
Doug