The layer properties allow you to set a symbol scale based on a fields value or an expression. This allows you full choice in symbology for the layer and the ability to symbolize differently by an attribute. However, this is seems to only work at a set scale. another option which works to a different degree is displaying by qantities with proportional symbols. However this only works with a single symbol, and can only be a cricle or square. I recommend a functionality that blends the both into one, where you can display proportionately, but have the option to choose any symbol, and be able to display by different symbols. Here is my example: I have a Manhole layer, with a integer filed which represents a size ratio for each point, so 1, .75, .5, 2, etc. I have the layer symbolized by status, so Existing, Proposed Addition, Proposed Removal/Retirement. I want to use the different symbols and size setting under Sybology by Categories but have the functionality of Proportional, so that the size of that symbol remins the same whenever the map scale changes.