Colour, layer and variations can be done with visibility states.
Scale? I haven't done that yet, but i'm working on it.
You can create dynamic blocks with AutoCAD 2007 LT, but not 2006 LT, that can only use them, or so I was led to believe anyway.
We use dynamic radiator blocks for varying sizes, and they just act like normal blocks to our older users.
They are so powerful, i'm working on a block which can rotate, scale and have visibility states, it's getting complicated really fast.