Some points:
[1] The roof at back of the North and South Stands is where all the rainwater from the roof is taken away to ground level. It is NOT a simple matter just to replace part of it. It is total replacement or an increase in capacity of a couple of thousand at the most.
[2] The gaps at the 4 corners of the group allow shutters to be opened to allow wind and sunlight to get in to improve water evaporation and grass growth. They have sunlamps on wheels to help grow the grass - but the draught is equally as important.