Some are pretty broad, but the Raynor building CP is a great question, as is, what if Bobby Jones didn't lose out early in the US am, allowing him to play CP as Mac built it, and thus chose Ross for ANGC?
What would architecture look like if there hadn't been a 20 year gap caused by WWII and the depression? What if the GA guys kept working and got to use bulldozers to a larger extent?
What would the average course built in 1980-2010 look like if Pros weren't so prevalent as design consultants?
What would the average course built in 1980-2010 look like if Golf Digest had maintained difficulty as the prime component of their top 100 list?
On a more personal note....
What would fees be like if courts hadn't struck down standardized fee charts?
Had Bruce Borland not perished in that plane crash, what kind of golf courses might he have built for JN, himself, or others?