The PROJECTNAME stuff always struck me as one of those ideas Autodesk had at one point, and they implemented some basic functionality that was useful, then they just forgot about it, and made no further improvements. This feature can still be handy from time to time, but it's enough of a pain that we don't use it often.
Autocad is designed to be used with one Profile. Having multiple Profiles is the way Autodesk set things up so we can run either "Civil 3D" or "Civil 3D as AutoCAD" and stuff like that, but your users really should not need to change user Profiles in the course of their normal work. And they definitely should not need to change Profiles simply to switch to a different Project.
I think the typical way of using this variable is to have one Project Name for each Project. I suppose you might vary that somewhat, if your particular circumstances dictate.
As far as offering your users a list, not really sure what you're getting at there. If it's what I suspect, then this gets back to what I was saying before, about how Autodesk implemented some basic functionality, then forgot about it. The Project Name list is stored in the registry for each individual computer, and there's no good way of dealing with it on a company-wide basis. Since this list is basically just a bunch of registry entries, you can create REG files that will create the list. Then you can simply tell all your individual users to run the REG file to update the list. It's really nasty from a "comfort" perspective, since it involves dealing with the registry and REG files, which also means it's version-dependent, and your REG file has to target the right version of C3D. But it's the easiest way I've been able to find for managing this list on multiple computers.
