Characters have always had a defined role in a group. The "archetypical" party of fighter, mage, cleric, thief has pretty much always worked better than any other 4 member party composition. It seems to me that all they are really doing is making sure that the other classes are reasonable substitutes for those 4 classes.
As far as your example of a guy that thinks D&D should be "run like a computer game", it's possible he simply thought that your players would have actually enjoyed it -more- if you did it the way the book laid it out. He may have even been right. Since you gave no actual details about the change made and the reasons for making it, it's hard to say.
I think mapping out encounters will do more good than harm. Planning out the actions of a group of 5-10 monsters isn't really an easy thing, and can slow down combat alot. Plus, it's sometimes easy to forget even the most important of monster special abilities when you are trying to get a combat moving quickly. It seems like the system they are working on will help overcome those problems.
As far as encouraging RP goes, that's one of life's great mysteries. People that like to RP are generally going to do it. People that don't, generally won't. Other games like Vampire(just an example) might seem like they encourage RP, but I suspect what they really do is discourage the people that don't want to RP from playing the game at all. The more a game talks about RP, getting into character, and stuff like that, the more likely your "rules only" types are going to close the book and never open it again. I'm not really sure there's much a game system can do to actually encourage RP.