I don't think your idea is at all out of line. I want to do the same thing as you do someday, but I have spent so much on my layout (which has both DCS and Legacy) and buying trains the last few years my budget needs a break. I have been looking at the NCE system, but the one you mention is pretty cool too. I watched some youtube videos on it a while back. I will probably just use some of my MTH PS3 engines to get started, however adding some Loksound and/or other brands of decoders to some engines someday is another thing I would like to try as well. I find DCC very interesting, not so much for the realistic sounds, but for the excellent sounds I have heard and the endless possibilities of settings to fiddle with. Who knows we may even up switching completely to DCC one day? 
As far as I know about the NCE system you need a remote, a booster and a power source. THe booster has a separate output for a 'programming track'. I have also read that the separate DCC programming devices are better to use and allow easier setups and changes and they also add more power than the Booster 'prog track' output which they say is especially helpful for decoders with sound. I have no first hand experience though, just info from DCC websites, youtube and reading about it. Sorry, I don't have much else to add to your questions, just wanted to let you know you weren't the only one interested in trying DCC like this.
