[Pamar]

When you say 1. You could have a table for every variant of the form do you actually mean one table for each version of the form, or more like one table for the 15 fields you care about+1 field for the form version # (sort of a base class) and then one extra table to capture extra fields when needed?

The latter is a sort of "inheritance" done in SQL and I had used it with good results in the past.