Changing the list formfield to remove the class "advancedSelect" if there are more than 10'000 options. Chosen has issues with so many options.
Changing the form to use the class "advancedSelect" so chosen explicitely is allowed on this element.
Set the formbehaviour.chosen to only act on selects with the CSS class "advancedSelect" instead on all selects.
This is the default behaviour for this function.