Well, I was hoping to discuss the concept on a more general level before going into the specifics of lists, but anyways, here goes, an attempt at an army list. Just an attempt, and a slightly radical one at that, I'm sure there are many other compositions that could work.
Marshal [General]: Blessed Armour of Frederick the Great, Crown of Scorn, Great Weapon [268 pts]
Marshal [BSB]: Hero's Sword, Hardened Shield [210 pts]
Marshal: Griffon, Great Weapon, Sprout of Rebirth, Shield [474 pts]
Marshal: Griffon, Great Weapon, Talisman of Supreme Shielding, Shield [494 pts]
Steam Tank [440 pts]
40 Spearmen: Command, Spears [460 pts]
40 Spearmen: Command, Spears [460 pts]
20 Swordsmen: Command [220 pts]
20 Swordsmen: Command [220 pts]
6 Knightly Orders: Command [390 pts]
5 Electoral Cavalry: Standard, Lances, Shields [220 pts]
5 Electoral Cavalry: Standard, Lances, Shields [220 pts]
5 Reiters: Brace of Pistols, Heavy Armour [200 pts]
5 Reiters: Brace of Pistols, Heavy Armour [200 pts]
4476 pts total.
The general and the BSB would go into one bus each, to cover each others' units under their radii of effect. The griffons, well, I thought, I'm running a tank, a prime target for enemy monster-hunters, one that can't feasibly avoid exposure to fire. Might as well go all out for target saturation and present the enemy with two tough, warded flyers. If the entire central formation needs to crash head-on into the enemy line, they can join in on that and lend their killing power and orders to the fray (with 4 marshals, all the infantry units could simultaneously Brace for Impact, for instance). If the situation instead warrants, the central battalion could spread out more, with the griffons where needed to beef up the line, or go on shenanigans of their own. The rest of the force is a mass of screening cavalry, for wiping out chaff and for counter-flanking attempts to flank the central battalion.