Thanks guys, both of you were a big help! Paradox, your solution is the one that seems to work best, but I appreciate seeing multiple ways of getting the job done, and it all helps me understand expressions a little more.
Update, I got things working just how I wanted! I didn't need the scaling to go all the way from 1 to zero, so I made some adjustments to make sure the scaling wouldn't be so drastic from bottom to top of the layer.
Here's what I got going
My layout is 720 pixels tall. I also wanted movement speed to scale down with the PlayerAnimation size too, so the illusion wouldn't be broken
System: Every Tick
-Set scale to (1/2160)*(PlayerAnimations.Y + 1440)
-Set 8Direction Maximum Speed to (300/2160)*(PlayerAnimations.Y+1440)
I found out that if I increased the denominator to 3 times the size of my layout, and added the remainder back to the PlayerAnimations.Y, I could keep the Y(720) yielding a 1 scale, while having the Y(0) yield me a .6667 scale.
Once again, thanks for all the help guys!