Good process and review.
On the topic of plastic glue: well, what's 'plastic'?

I strongly doubt the Shapeways FUD is much like polystyrene, or that poly cement would have much effect on it.
I haven't had first-hand experience with FUD, so I can't say for certain, but I still doubt it.
On the topic of newbies scrambling for a copy of sketchup: I can't help but think you're barking up the wrong tree, just a bit. 3D printing is already a big part of miniature sculpt production, but I don't think it'll be entirely the brave new world of hobbyist power, creativity, and cottage industries that seems to be the general impression. Not much more than when (widely-available) putty was pretty much the only option.
Symmetry and undos are advantages (trad sculpting already has an undo, though: it's called a knife), and there's no doubt it's a great system for straight-edged mechanical objects. But I think the more organic you go - if branching out beyond square gun bits - the less you'll be able to rely on the medium to do (some of) the work for you, and the more you'll have to fall back on and develop your own skill. And how many were willing to do that with putty? I have a feeling it could surprise some people, how difficult it might be to replicate even Space Marine powered armour, without much experience.
Not to discourage anyone, but it might help to keep in mind the fact it's not a magic wand.
On a related note:
Y'know what you get if you pay peanuts?

I'm not getting how cheap it to produce masters, though. What makes it cheaper than a packet of milliput and a wax 5, or paying a trad sculptor?