Commenting post 6: Hi Phil,
Interesting. I also think IFC is definitely the way to go. Most IFC assets you'll find in online repositories like bimobjects.com are of not very good quality, mostly because they are all triangulated. However, the IFC format has almost all geometric powers of STEP, there is no reason it couldn't convey high-quality geometry, besides the lack of proper implementation from these repositories IMHO (IFC has a complete NURBS model, there is virtually no surface type that cannot be faithfully represented).
That said, Revit's ability to deal with IFC file has serious limitations, and what most Revit users will consider "a proper asset" is something they can squeeze and stretch or that contains several options in one same family/asset. Which very unlikely you'll be able to do with IFC (not that it couldn't, but there is a huge gap to fill before these things are widely implemented in host BIM applications).
So you might not have Revit users fully happy there. And you probably won't ever unless you give them .rfa files fully modelled with Revit. But that's exactly where the problem lies, you would tie yourself almost exclusively to autodesk ecosystem, and your models would hardly be very good outside Revit.
I believe the way is to provide high-quality IFC models, fully tested with Revit for geometry quality and "familyness" (the ability to use your IFC object as a family, a tricky issue), and with all the necessary properties, attributes and other non-geometric parameters nicely set. If one product has several options, instead of an "intelligent" revit family with drop-down options to choose, it doesn't seem to me a big issue if you provide one model for each option, as long as it is easy for the user to switch between them.
As with everything open-source (and not), documentation is a key. Together with your models, if you have carefully crafted documenation on how to use them with the different applications, I believe the advantages quickly outweight the issues, from a user point of view.
About MVDs, honestly up to now I haven't found much application for them. If you concentrate on the basics (clean and simple geometry, standard sets of properties), I believe you obtain models that are pretty "MVD-safe" and would basically "pass" all the requirements of the different MVDs.
Sure, I'd be happy to help if needed. Under the top right icon of this page, there is my email address if you prefer.