Dan,
When I went to Killian and Nugent's office as a 12 year old, they told me about the same things. They recommended a main course in landscape architecture, supplemented by studies in agriculture/agronomy, "natural systems", soils, and drainage. They added surveying (just in case Seth Raynor wasn't still available!) and study of aerial photos, because thats just how we roll these days. Now I guess it would be GPS.
They also recommended business, sales, and business writing classes, and any engineering classes I could take. (too tough as it turns out, but I took a class in the ag dept that covered soils, drainage, and surveying and got all I needed.
It served me pretty well, and I have continued my edumacation, with environmental classes, CAD classes, legal classes, etc. Somewhere along the way I picked up some land planning skills, too.
If they had really seen the future, I think they would have recommened training in dealing with internet golf architecture groupies, which going forward will be the key to the whole deal.
Knowledge of golf is a given, and probably overplayed. Since the days of McKenzie, average golfers who love the game have been able to create great courses. If you can't do it with the technical backup to really make it work, you aren'tr eally a gca. You are just playing in the dirt. Just MHO