The commissioners shall not be confined to the point of commencement, route or terminus of any drain or ditch, or the number, extent or size of the same, or the location, plan or extent of any levee, ditch or other work as proposed by the petitioners, but shall locate, lay out and plan the same in such manner as to them shall seem best designed to promote the public health or welfare and to drain or protect the lands of the parties interested with the least damage and the greatest benefit to all lands to be affected thereby; 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.