Can I build a six-week schedule from six different weighted historical index forecasts?

Unfortunately, no not at this time. A single schedule can be created from only one forecast at a time.  Because of this, schedules generated using weighted historical index forecasts are limited to one week in length. To take advantage of six-week scheduling, the automatic best method selection or import forecast creation methods are required. For more information, see Generate a schedule from a short-term forecast.