Mike,
Let's see if I can answer your questions.
You observed, "The most obvious ones for me are the two par 5's, #4 and #13. Neither are reachable from the back tees (at least I don't think so) but a move to the forward tee on #4 could make it really interesting since the green is protected by a big bunker in front, the green slopes away from you, and there is a huge dropoff behind the green. You would have to hit an absolutely perfect approach shot to hold the small green but it would be exciting to watch."
# 4 will only be played from the upper championship tee. The reason for this is that a number of players, including one of those in tomorrow's playoff, would consider going for the hole in two. Remember, it is only a 540 yard par-5 with a banked landing that shoots the ball forward and downhill. It is because no one will be going for it in two, the unanimous reason being the green sloping from front to back, that a planned further back tee was not built.
You observed, "On #13, the cross bunker is about 30(?) yards in front of the green, playing it at a distance that would make reaching in 2 require a perfect drive and fairway wood would really create some interesting decisions (much more than #18 at Torrey Pines, where it seems like almost everyone can reach)."
A new back tee adding some 65+ yards in length was added. I wouldn't be surprised to see a combination of hole lengths of the up tee of 595-600 and the new back tee at 660-670 used.
More interesting is a VERY new suggestion of playing 7 as the par-five that it was originally designed at from the original championship tee. It is 600 yards from there and there was a new tee that will make it a par-4 of 525-530 yards, about 30 more than in 2002.
You observed, "#6 is also a candidate with the ability to cut the dogleg and get it down right in front of the green. The par 3's are all different lengths so I don't see moving them back and forth as making much sense."
#6 will not have a forward tee. They have cut down the rough on the face of the downhill side of the slope. This is being done to encourage players to try and fly the hill.
You observed, "#17 would play much differently, obviously, from the front tees at 175 than all the way back at 220, maybe a front tee with a front left hole location would be a challenge."
I would expect some change in tee location but nothing that would be overly dramatic.
The bigger change will be at #14. I would expect to see a front-left hole location in the new tongue played from a far front-right tee. This will be a diabolical 130 yards. With the tee box approximately 20+ yards wide and 30+ yards long, and with the back and right portions of the gren also recovered, a wonderful choice of angles and distances will be available to choose from.
The 9th hole has three changes to it. The new tee will add length and, combined with the new bunker built across the face of the upslope to the second plateau, will make a player trying to reach it with their drive a real risk/reward decision. In addition, the fairway is being cut much firther to the right and into the existing rough area.
The 10th hole may be shaped differently than in 2002 with a decision to shift the fairway to the right in order to bring the bunkers back into play being considered. The same idea is also being considered for 11.
The 15th has the original far back tee built but never used for 2002. It's use is still being debated.
Also, a bit of distance has been added to 16 with an extension to the back of the tee box.