as of version 1.4 you can dynamically change the (most) options you have set in your options settings page.

as an example, you could have set your options to allow pre-ordering to be 3 days in advance.
however, maybe you do NOT want to allow preordering on a friday and saturday , so you could do the following:

add_filter( 'wppizza_po_filter_options_get_dates_and_times', 'myprefix_wppizza_preorder_set_advance_days_by_day' ,10 , 2 );
function myprefix_wppizza_preorder_set_advance_days_by_day($options,$timestamp){
$getDayOfWeek=date('N',$timestamp);
/**do not allow preorder on friday / saturday -  outside opening hours */
if($getDayOfWeek==5 || $getDayOfWeek==6 ){
$options['options']['days_in_advance']=0;			
}
return $options;	
}