Nice idea about reordering properties to improve gzipping. I don’t think a fixed ordering (e.g. alphabetical) will be optimal, however. Suppose I have the following:

body {
color: blue;
border: 1px solid red;
padding: 10px;
}

div {
border: 1px solid red;
padding: 10px;
}

Changing the order of border and color in the body will decrease the repetition and so increase the gzipped size.

An optimization technique (something in the realm of genetic algorithms) could be used to determine an optimal ordering which would be unique to the particular source file.