I just finished hacking together a mod of QuadParticleSystem that allows a particle to scale over time on the X or Y axes.
I did this because I wanted to have a falling stream of spinning coins (flipping end over end). What the code does is lets you set a percentage to scale the X and Y by each step, and a percentageVar that allows you to vary this amount per particle. It's currently set up so it never scales over 100%, just keeps flipping. This is fairly different from the way other parameters work, but it fit what I needed.
It's working great, but my code is a really ugly and hacky. Is this something other people would be interested in? If so, I could clean it up and submit it, but I've never done that before and this is pretty specific stuff, so I wanted to ask before I spent the time.