Personally, I think that a 5 par 5/par 3 layout would be a fresh change of pace, although maybe not necessarily as an industry trend. In my mind, par 5s, depending on length and setup, can either provide a realistic birdie opportunity or a realistic par opportunity for say the 90s shooter. Reason being, par 5s allow for you to make a mistake on at least one shot and still come away with a respectable score. In addition, I am of the opinion that most players prefer to play a par 3. For one, and I am not saying I enjoy this, they often provide the most aesthetic value on today's modern courses. Plus, they can be made relatively short from the middle tees so as the average player only feels he needs to make one good swing which provides him confidence. If at least two of the par 5s are made long enough so as to not be reachable at all, I think par 5s have the most otential for strategic value. For one, you would need to make three good swings, each one building upon the quality of the other. In this sense, angles may again become important in the modern game. As far as balance, my ideal course layout for such par values would be as follows:
par 3s of about 120, 160,180 210, and 240ish from the back tees.
par 4s of about 320, 390, 410, 410, 460, 460, and 480.
par 5s of about 500, 500, 540, 590, and say 610.
I think such a layout would provide many opportunities for birdies as well as afford the ability for at least two par 5s to be turned into long par 4s for important tournaments. Such a golf course if designed with the proper angles and variety as to shape and wind may infact be very interesting to play.