Yes that is one way to deal with things or get resistant strains of melons.
Have doubts watermelon grafts would take on Cucuzzi.
Using the original links i posted you can isolate the strain of wilt. Plant a tomato resistant to f1 f2 but not f3. Then plant one resistant to f1 f2 f3. Then plant one resistant to f1 only then you know which strain you likely have. Ideally it would be best if 3 plants were only resistant to one fusarium wilt but i doubt that is possible. Once you determine which fusurium your dealing with you will have no problems in the future.