It would be nice if symbol sizes (and associated labels) could be driven by scale. Right now the only solution I'm aware of is to create different layers with different symbol sizes that appear and vanish with scale dependencies. I realize the Reference Scale option was likely created to try and address this issue, but ideally I'd like to be able to control a single layer's symbology independent of any other layers in the map document.This would be extremely useful for me with AGOL/Collector applications.
An example would be transmission structures; at something like 1:100k these would be small dots, at 1:50k larger dots, at 1:24k a larger symbol with a label, and then at 1:5k very large symbols with a masked label. I know I can do this with 4 layers, but being able to do it to a single layer would be great.