Ben,
I agree with the premises that length is getting out of control (8000 yard courses?) and that having more courses around 6000 yards could be a good way to allow more people to play.
But, I wouldn't want to get stuck on formulas. For example, I totally disagree that architects should avoid building 325yd-425yd par 4s. I love a good medium length par 4. So what if they benefit long hitters? Length should be an advantage. Of course, ideally such holes require some strategy so bomb and gouge doesn't always work best.
As a mid-handicap (9 and trending upward), I would hate to see courses have 6000 and 7000 yard tees with nothing in between. My ideal distance is probably between 6400 and 6700 yards but shorter courses, particularly ones with elevation changes, and some longer courses (up to about 7000 yards) suit me well too. Obviously wind can change everything.
I'd favor more courses around 6000 yards and with a par under 70. In my mind, the key impediment to playing more golf is time. With the equipment now, it's never been easier to hit the ball long and straight. But many people can't take 4-6 hours (with travel) to play golf frequently. So I'm less concerned with making it easier for higher handicaps to hit greens in regulation with short irons and more concerned with making courses that take less time to play (i.e., more compact, sub-par 70 courses).