WebPlayer Custom Params Inspector

In the WebPlayer Template index.html i can define %UNITY_CUSTOM_XXX% parameters, which appears in the PlayerSettings Inspector-Window as string fields.

Its possible to override them with a CustomEditorScript, so i can use other fields for the UnityObject2-Parameters? (e.g. bool field for disableContextMenu, image field for logoimage, or other script calculations)

Which type of class i have to override? Or is there any other possibility to set these parameters from the inspector?

thx.