Complex sentence: Sears executives decided that the space they would immediately occupy should be efficiently designed to house their Merchandise Group, and that floor space for future growth would be rented out to smaller firms and businesses until Sears could retake it.
Split into simpler sentences: Sears executives decided that the space they would immediately occupy should be efficiently designed to house their Merchandise Group. But floor space for future growth would be rented out to smaller firms and businesses until Sears could retake it.