Well, in general it is possible to paste the HTML of an existing Diagram into the Play-Test Applet, and then use the GAME code button. But this only works for 'run-of-the-mill' variants that the Play-Test Applet could generate. (I.e. pieces that move differently, but otherwise normal rules.) Promotion restrictions, multiple royalty or anti-trading rules can be added by post-editing of the generated GAME code (modifying or adding some tables).
I am not sure if all your variants are of that type. When the ID required custom JavaScript, no GAME code will be generated to perform its function.
Well, in general it is possible to paste the HTML of an existing Diagram into the Play-Test Applet, and then use the GAME code button. But this only works for 'run-of-the-mill' variants that the Play-Test Applet could generate. (I.e. pieces that move differently, but otherwise normal rules.) Promotion restrictions, multiple royalty or anti-trading rules can be added by post-editing of the generated GAME code (modifying or adding some tables).
I am not sure if all your variants are of that type. When the ID required custom JavaScript, no GAME code will be generated to perform its function.