This may exist in various places and to various degrees as add-ons but my 'ideal' material interface would offer:

1. 'Complex' complete presets e.g. cracked concrete with rusty reinforcing rods etc.

2. 'Basic' presets e.g. metal with the ability to drill down and refine the material e.g. steel or platinum etc. and then be able to specify additional parameters in everyday terms, e.g. scratches, rust/corrosion, polished. dull, color yada yada. The same would go for plastic etc. with appropriate parameters. If you can give me oil stains or water driven by a distribution map, even better. I'm not necessarily interested in exactly duplicating plastic X with complete physical accuracy, just create say a pill bottle by chossing plastic and setting the color, translucency etc. and have it be reasonable. I would hide the numbers as much as possible - leave that to the advanced interface or a tooltip. I think the combination of numeric inputs and terms many don't really understand plus relationships between parameters that many don't understand makes the wole exercise seem hopeless for the less sophisticated. It may seem overly simplistic to have min/max sliders and terms like transparent and mirror-like instead of set ansiotropicana to .019, but I think I'd grasp it better.

"...Vue's shader system is easier to understand than Poser's..."

I agree. Whether deliberately or not, they seem to be less oriented towards the TD end of things. The realtime render thumbnail scene preview helps tremendously in seeing the result of your adjustments, but that's another story. I also agree that simple(r) DIY isn't necessarily a contradiction. It may well be that trying to 'tame' a node based system by constraining connections, adding some kind of sophisticated AI etc. might be more trouble that it was worth. I'd start with a clean slate and look at some other applications in designing a new basic material interface. I simply think that node based interfaces are less than ideal for casual users. I'm sure many will disagree. I throw up my hands whenever I read someone who says their demented great aunt was up and hacking the command line in RedHat Enterprise in two hours as well :-) I'm sure that the technical challenges of doing something different vs. the perceived benefits mean it won't happen, but I remain convinced that it would be a boon to a lot of people.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken