I've resized physics objects before with no crashing
it didn't work when I tried it just now though
I guess it's pretty touchy
anyway, for now though if you don't mind the collision mask thing
you can have a non physics object follow it around
here's an example with some random emission stuffs
and growing particles with physics
http://dl.getdropbox.com/u/1013446/particlephys.cap
you can store the current color filter for each sprite in a private variable and you could do the color ramp as well
btw, if it runs super slow on your system, cut down the fade out time on the sprites, it should make it run better