Kind of like kit bashing, yes. Only you're not taking parts of other fleshed out models, just using primitives which are free to use by everyone. With the grouping tool you can extract individual polys from those primitives and then put them together with other polys. Scale, translate, etc, export and reimport so that they're one object. I'm not sure what you'd do for UV maps tho, as its been too long since I messed with it. Would have to use procedurals instead I think. Or just solid colors. Or just use a program that's actually meant for full modeling. But the point was that you can make custom models without leaving poser, though it's not very practical and there are better, easier ways of going about it.