I've requested this before using the Adobe feature request (probably many years ago now) but I thought I'd try it here and see if there are other people who also think that this would be a great and valuable addition. I also know that people from the AE Dev Team have been known to respond on here.
Basically I think it'd be *SO* useful to add a String Control effect.
So in other words you could go to Effects>Expression Controls>String Control
This would allow you to use a single expression to generate a complex data result. You could then reference this string in other properties and extrapolate the data within it. I have lost count the amount of times I wished this was a feature and it would massively help complex, expression-heavy projects.
I've used a text layer to kind of do this. I just made a text layer, and the text value was generated by an expression. Then other expressions elsewhere read the source text in that text layer and use it one way or another. It was a while ago, sorry I don't have code.