JAB I agree with you on a couple of points, particularly the "reckless yet eager" and "mature yet controlling" comparison. I agree that allowing for younger GO (and Command Sergeant Major) leadership might change the culture of the force as far as risk aversion. I mean McMaster was fairly young to become a BG a few years ago, was passed over twice in 2006-2007 (even with his Desert Storm and OIF 1-2 Tal Afar success) until Generals Petreaus, Austin, Ordieno, etc took over the promotion board screenings, and still hasn't been given Division Command even though he made the 2008 list. He's going to be 50 next year.
However, the leaders you mentioned all held critical jobs in their younger days of soldiering that prepared them for high command and do not agree on your comparison to the generals of ancient times. Given the nature in warfare at the times they served, I believe that Washington, Grant et al can be ranked up there with Caesar, Napoleon, Alexander. Additionally, those four you mentioned were hardly less risk averse. Washington had to be talked down by his staff and subordinates from trying to do a decisive blow on the British multiple times in 1776 (ref. David McCullough's book 1776), Eisenhower blessed off the invasions of North Africa and France, Grant was ruthless i.e. The Wilderness campaigns, and the Inchon landing was MacArthur's brain child. Of note, BG Teddy Roosevelt Jr was 56 years old when he led the 4ID on Normandy beach in the first wave.
I was thinking more along the lines of someone like General James Gavin (mid-30's when he commanded the Eighty-Duece) and General Matthew Ridgeway (47 when made a Division CG). I think good, competent, successful, combat tested, leaders should have a shot to make Division command and Division CSM by the time they reach 20 years in service (maybe even 18 years?!).
And speaking of risk aversion....my Dad used to tell me stories about the KIA list being 400 guys a WEEK during some of his time in Vietnam. Nowadays the press goes nuts if we lose 100 a month. It's sad that it happens and it's tragic but I also believe that we shouldn't be so risk averse that we put the mission behind the "I'm going to get everyone home" promise. It's false promise the moment it leaves someone's lips but I've heard it way too many times from BDE and BN commanders saying it to their Soldiers and their spouses. The enemy has a vote and yes we should be ruthless with negligence in the field (ref Wanat and COP Keating) but let's not tarnish the honor of our dead by shirking the mission just because guys might get hurt.
Just my two cents as a Captain with 6 years in....