Over-commercialization will kill them in the long run. Lego was great in its old series' as it left all the details up to the kid building it. Sure, there was the generic king, but everything else was up to the imagination. If I want to play with lego wizards, I don't need blinking Harry Potter!
Next, although some of the modern components are really cool, a lot of the old ones were equally great. Over-simplifying parts will also be a turn-off to advanced builders who need those, perhaps less durable but all the same, small, complex parts like the old hinges and whatnot.
As far as great user-made kits go, I thought they had a system a while back where you could make your own sets online and then order them, but goodness knows that's probably horribly expensive. Lego was never cheap, and now that I think of it, again, that commercialized crap isn't helping!
On a secondary note, if you need interesting parts in bulk, get a few Mega-Blox sets - that's always fun.
