Thanks for the response, Cyanstudios.. but I'm not sure I understand what it is that you're trying to do... what is the bigger picture you're after?
* Everything in one application - this is a white unicorn. Autodesk has a huge infrastructure of many products. Some workflows lend themselves better to desktop authoring (such as Revit), some lend them selves better to Tablet based workflows such as point layout or status tracking, and some lend themselves to collaboration across stakeholders (Glue).
* Parametric relationships and flexibility - Can you say more about that? In some cases, Revit historically has been too restrictive in this way... e.g., even if you could build in the flexibility that a sheet metal fitting offers into a Revit family, to get a parametric solid duct fitting or segment in Revit out to CAM, there was various translations and mapping that may or may not match exactly what was in the shop, causing Re-work. for example, the length of a decoiled duct segment is driven (parametrically) by the type of connector (e.g., TDC or S&D), and further, what the tolerances for these are in the specific shop's equipment. Integration of Fabrication ductwork in to Revit provides a direct path for Sheetmetal modeled in Revit to go to shop production. Further on the flexibility route, having Pipe fittings that can bend to any angle, as Revit design content is intended to do, doesn't lend itself to real-world catalog items that be procured and prefabricated in the shop.
* Total control over geometry and data - this doesn't really sound like a goal (again, over-flexibility can be a bad thing... e.g., everyone naming parameters differently is certainly not conducive to automation nor rationalization of model data). What is it that you're not able to accomplish?
* Integrated - what is it that you're trying to do? A model produced in Revit can be sent to any other Revit user (well, as long as they're on the same version or later <grin>). There are reasons users don't want all data transmitted (e.g., a contractor doesn't necessarily want all their cost and labor data transmitted to GCs or other Design Firms or indeed other Contractors that they may be collaborating with.)
we certainly need to understand the problems you're trying to resolve... the specific examples you've cited in your original post are solved, but I'm sure there are others where reading the main segment's size would be beneficial, so let's bring them to light so we are aware of them.