If I understand the current limitations correctly, this would be a Holy Grail for managing different object libraries and still producing standardized information for scheduling and export to IFC.
A generalized example. Window objects from different manufacturers obviously store their technical information in different gdl parameters (say fire rating for example), as there is no standard for parameter names. Now, if I could set up a formula using if-statements that checks the object name (or part of it) and based on that information maps the correct gdl parameter with appropriate text formatting functions into a general, standardized element property for all windows, this would be revolutional for managing scheduling and export in projects with objects from multiple vendors.
In the current world of BIM this type of functionality should already be available. GS talk up BIM like they have is all sorted "BIM in an instant" is the 23 marketing blurb.
But as you have mentioned here if you actually want to access a bit of BIM information from an object and use it in a calculation you simply can't and don't start me on the amount of clicks needed to get to the data in the first place!
I like the idea around the properties structure and the expression builder but its implementation in a workflow is less than ideal. For one, the 'schedule' structure is the wrong way to go to extract data instead the 'list' functionality needs to be built upon so that each element can have a multiple records stored against it rather than one record with a multitude of columns.