How can I scale particle size over lifetime within a keyed physics system I am trying to make an alka-zeltzer in a glass, creating bubbles that form a logo on the water surface. To do this I am using keyed particles and everything works fine. 

However, I would like to have the particle's (object) size scale over each particle's lifetime. This is where I fail. I know the trick using a texture block with a color blend driving the particle's size, maybe against an object for mapping. It seems though that when using keyed particles, this is just ignored.

I'm wondering if I can get to a driver for the particle lifetime or age, as they must exist, because they are available as outputs on the particle-info node within cycles.
Maybe I'm getting ahead of myself. This may be particle nodes territory. Is there a way around this?
Currently it is not really possible to drive particle size with a driver. One can drive them so they show in the 3D View with different sizes, but the render engines (BI and Cycles) don't see the size changes, unfortunately.

See the report in the Blender TODO tracker here: http://projects.blender.org/tracker/?func=detail&amp;atid=264&amp;aid=34946&amp;group_id=9 . Some examples are included.