I've been tossing the idea of an Engineer army around for a long time. The army would focus on being a modern and mechanized force, by Imperial standards, much like Lord Cromwell's 'New Model Army' during the English Civil War and the wars with Ireland.
Here's the list:

Lords: 244/625
ArchLector w/ Armor of Destiny, Van Horstmans Speculum, Sword of Battle, Barded Warhorse, Shield
@ 244 (Joins Knights)

Heroes: 514/625
Warrior Priest w/ The Silver Horn, Heavy Armor, Shield
@ 131 (Joins Handgunners)

Warrior Priest w/ Casket of Sorcer, Heavy Armor, Shield
@ 131 (Joins Handgunners)

Captain BSB w/ Dawn Armor, Talisman of Protection, Barded Warhorse, Shield, Halberd (Joins Knights)
@ 145

Master Engineer w/ Mechanical Steed, Repeater Pistol, Light Armor
@ 107 (Joins Pistoliers lategame)

Core: 665/625
10 Empire Knights w/ Greatweapons, FC, Banner of Arcane Warding
@ 300

19 Handgunners w/ Marksman, Standard Bearer, Repeater Handgun
@ 182

19 Handgunners w/ Marksman, Standard Bearer, Repeater Handgun
@ 182

Special: 461 – 625
11 Pistoliers w/ Mus, Outrider, Repeater Pistol
@ 222
10 Outriders w/ Musician, Champion, Hochland Long Rifle
@ 239

Rare: xxx/625

total: 2,484/2,500

I think that the army is going to be deadly, if not just borderline cheesy. The idea is to shut down enemy magic (+4DD) and then coordinate my army to both shoot him to death (103 shots/turn, plus Steam Cannons), and overrun his regiments in close combat. I have no qualms about reforming my Handgunners and charging the enemy if I have to.
To keep the army respectable, I do intend for it to be very conversion heavy, and really look the part of an elite army created and funded by the College of Engineers.