Ben,
To answer your question, I would definitely give up the front nine of meadow-valleys. Although I think 2 and 4 are good holes, and 5 and 6 are fun, the flatness of the land makes this nine the least unforgettable, most manufactured and (for this reason) have more Pete Dye repeats than the other nines. The only caveat I have is that the original 1 should replace the awful 10th on the meadow-valleys course, which I think is the worst of all. Like 14 on the River course, it seems to have been stuck there for routing reasons.
As to the 14th, I agree that after the very difficult stretch, it seems to be a breather which can jump up and bite. There are a few holes that seem manufactured on the river course, and all of these seem to date from the original routing. 2 and especially 4 also seem manufactured on less-good land near the clubhouse, and I don't particularly care for the mounds between 1 and 2. Good holes, just more fitting with the front 9 of meadow-valleys. Wouldn't the best be the original 1 and 12-18 meadow valleys, 5-13 river with 16 tucked in there somewhere? Not much of a routing, but the greatest holes. In any event, Tom Doak's book states that the land where 5-13 came in was originally made off-limits by Mr. Kohler, so it couldn't be used.
Jeff Goldman