This may sound like heresy, but I believe the Captain and Engineer would be better merged into the same unit type. Right now we have Wizards, Priests, Captains...and Engineers. And the last choice is relatively redundant. With many of the more recent armybooks anyway, we have our "Fighter; Caster; Special" set of heroes, be it Masters/Sorceresses/Death Hags for Dark Elves, Chieftans/Warlocks/Assassins for Skaven, Saurus/Slaan/Skinks for Lizardmen...really Chaos seems to buck the trend...With Empire, we have our Captain/Wizard/Warriorpriest combo, while the Engineer does not get invited to their parties.
With prior discussions, we had expressed interest in making the Empire Captain your "down-to-earth" type, having abilities that did not correspond with magical prowess, or religious blessings, but instead the result of superior training, better equipment, etc. So why not merge the Engineer and Captain/General (And merge the Templar Grandmaster into the mix, while we're at it)? Put assorted "The Imperial College" abilities into the greater list of non-magic upgrades the Captain/General can take?