Doug
Primarily most of the changes have been inintiated by Mr. Vickers. He talks with Jack and they either agree/disagree on a potential modification. Mr. Vickers reasons for changes have be driven mostly by a desire to host a US Open. He has consulted with USGA officiials over the years on what the course needed to be considered. The equipment "improvements" over the last few years have had a dramatic impact on the course especially since the ball carries about 10-12% further at its elevation. For example, the 8th which you mentioned was being reached by some of the longer hitters in the tournament with 6-8 irons, thus his desire to find a back tee. The 17th is frequently reached with 5-9 irons by most tour players. Thus, he has built a tee on the other side of the pond, although it has not been used to date.
Mr. VIckers wanted to rebuild (lower) the 8th green and he pretty much knew what he wanted to do. Jack wanted to rebuild the 4th green and he drew the plan. My involvement thru the years has been to implement the changes the owner and designer wanted to make. I think all, even the 8th green is an improvement to the original, of the changes have been well received and appropriate.
The 14th pond/stream is awesome IMHO. Again, the hole is over 623 yards long, and although downhill, was originally designed to possibly run a second shot on the green avoiding the left bunker. Charles Howell recently in the tournament, flew a drive and 7 iron on the putting surface. The pond was introduced to at least put a premium on second shots, since all players would just fire it at the green and pitch and putt. The hole now with the pond/stream makes it one of the most attractive holes you will find anywhere, again JMHO. There have been many other changes thru the years, but over the past 3 years CP has embarked on regrassing 3-4 greens a year to eliminate the poa annua encroachment. We have taken this opportunity to modify if the owner/designer agree to do so. Hope this answers most of you queries.