I strongly suggest that there should be a "light" version of the CSS plugin. Yes it's only 15k gzipped, but the filesize that is accounted for when publishing is the non-gzipped size. We often have a 150k limit with banners, and most of the time the designs we have to animate have transparency... we therefore are stuck with using heavy 32 bit png images. Every bit we can save on scripts is a bit we can use on images. For that reason, we were forced to program our own "plugin" for banners, since we cannot afford to include the CSSPlugin, but it's certainly not as robust as we wished.
Since banners are html5, a css plugin with a limited backwards compatibility would save space. Also, maybe a subset of the properties we can animate would suffice (I'm thinking scale, rotation, opacity, position).