I'll have time to work on this come Tuesday, but it would be helpful if you could pull together a list of actions that you'd like to see before then. It would also be helpful if you could be as descriptive as possible about each one that way I don't make the plugin in a way that seems fine to me but odd to others.
Ok, I'll give it a shot - surely others may have ideas as well, but here's how I'd see it (having taken a big knife to the initial description and trimmed off all the fat):
I'll use a mockup of how it may look in the editor, seems to help with describing it. So Anyhow:
Basically like the Fade behavior, but for Scaling. Let's go over the options:
Activate at startup - same as Fade.
Scale over time - if this is greater than 0 then it's an animated scale and you set the time in ms to go from current size to the new one.
Horizontal Scale (px or %) and Vertical Scale (px or %) - this would be the meat and potatoes right here - if it could understand % then there's no need for a separate proportional scale behavior - just set both Horizontal and Vertical Scale to, say, 150% and you get proportional scaling.
Set the size in pixels and it scales to that (up or down, as needed).
Destroy afterwards - same as Fade. So you could have it scale to 1 px and then disappear. Or combine with Fade, scale to 200% or more and get some nice puffs of smoke.
Show in Layout Editor - Not sure if this can be done, but it would be cool - check this to see the end size of the scale - would help with some decisions without starting the layout all the time.
Now onto the editor side:
I'm not sure if a separate Set Up window is possible, looks like all the Behaviors so far use single-link settings. So just a mock-up for that. Should work the same here - enter scale in pixels or %, etc.
As for Conditions - not sure if On Scale start is necessary, since mostly it would already be there because of some event. On Scale complete could be useful, though.
Well, that's the idea - hopefully it's not looking too imposing and not too much like terrible linkman exploitation on my part I'd gladly help with something within my skillset (mostly graphics work), that's for sure.