You may just have uncovered a niche for somebody to develop for. I've used a lot of 3d graphics programs, from the text-based POVRay through Blender, 3dsMax, Maya, SoftImage 3D and the quirkier stuff from Daz. They all have steep learning curves, and except for the FOSS family (which have a high entry point from a usability perspective) they're pretty expensive. Like good, fast, long glass expensive -- certainly more expensive than you'd want to pay if you then have to spend a month learning how to do the basics, create stored light objects (different sotboxen, reflectors, grids, barndoors that obey the laws of physics, lights with different power characteristics, etc., that won't let you simulate perfectly something your gear can't actually accomplish).
The one truly usable-out-of-the-box app, Caligari's TrueSpace, is Windows-only and orphaned since Microsoft acquired them, but it is a free download. Unfortunately, the online tools and tutorials mostly refer to a feature set that was cut from the free version, but you can still accurately model lights, reflectors and so on. There's also a free "learning edition" of Maya, but the ability to save out objects for reuse is either missing or extremely limited (perhaps the one time I managed it represented a bug in the crippling code). Too bad, because Maya does lighting very well, and you don't really need high-rez unwatermarked renders for this application.
If you want to go the 3D simulation route, then the most cost-effective option would probably be Blender. It would help considerably if you could find, create (or, preferably, have created for you) a standard set of lights and reflector panels as objects you can just add to the scene, then drag around and play with controls that mimic the ones actually on your gear. Unless you're in it for the curiosity, there's too high a frustration factor in building the world from the ground up every time.
All that being said, though, there's no substitute (yet) for a mannequin (or an assistant). Even a grey-painted styrofoam wig head on a light stand will tell you everything you need to know to get the broad strokes right, then you can just do minor refinements when your model/subject arrives. (Or major refinements if your subjects are much like the real people I used to work with -- sometimes it's all about lighting that one good eye perfectly and letting everything else fall into shadow, you know?) And for just playing around with ideas, an "action figure" or two, a couple of flashlights, one small sheet of one-stop ND gel to selectively lower the output of each light, and tabletop tripods (the cheap ones the sell at non-photography stores) will let you noodle about quite effectively without wasting anyone else's time.