The commissioners shall not be confined to the points of commencement, routes or termini of the drains or ditches, or the number, extent or size of the same or the location, plan or extent of any drain, ditch or other work, as proposed by the petitioners, but shall locate, design, lay out and plan the same in such manner as to them shall seem best, to promote the agricultural interests and to drain, or to protect the lands of the parties interested with the least damage and the greatest benefit to all lands affected thereby. And any plan proposed by the commissioners, may on the application of any person interested, on the hearing hereinafter provided for, or on the application of the commissioners, be altered by the court, by written order, in such manner as shall appear to the court to be just.