I’ve thought of another solution that could help you with your situation. If you are using Denodo 6.0 or a recent update of Denodo 5.5 (20150319 or newer), view parameters from underlying views will be used for searching only, but not for filtering when queried in a UNION view. This is the functionality you want, but it only works in situations when the column you are specifying in the WHERE condition is a view parameter, not an interpolation variable as is the case in your situation. However, this provides a new solution.
To implement this, consider views A, B, and C as described in my previous comment:
1. Build a derived view on top of View B.
2. Add a view parameter to this derived view for each interpolation variable you have in View B. In the WHERE conditions window, set each interpolation variable equal to each respective view parameter.
3. Create View C as union between this derived view and View A.
At runtime, you will be asked to provide values for your view parameters rather than your interpolation variables. The values you provide will be used for searching, but not for filtering. Thus the tuples from View A will not be filtered out.
Hope that helps!