Thanks! I've been building lists on BattleScribe with this idea in mind and I have included Ludwig, a warrior priest, and a Bright Wizard in the list, with a witch hunter if I can fit it. The rest of the army is pretty much 2 handgunner units (I can break them up into detachments if needed), 1-2 units of halberdiers, a unit of swordsmen, a unit of greatswords, Reiksguard, Knights of the Blazing Suns, a couple of cannons and a helblaster volley gun.
Karl takes up a lot of points and in more conservative games I'd theoretically take Kurt Helborg instead. I'm broke AF right now with enough Horus Heresy miniatures to paint to last me a while, but when those projects are done I am thinking of starting up the old empire. For the first time too. I am at a lost on which edition everyone has been using since End Times blew everything up. I have the 7th edition Empire army and rule book handy though.
Not sure how I feel including a unit of Stirland or which of the units I mentioned would be them, and I've been leaning toward a mostly Reikland army with maybe a couple of Altdorf units like the helblaster. I guess the idea is for the army to be Karl's quick response army to threats to the Empire, supporting the other Electors' armies with his war host. But what should his warhost be? Reikland or Altdorf, or both?
Edit: I went through the 7e army book, wow. Why does it seem so sparse? No Witch Hunter or Reiksguard Knights? 8th on Battlescribe had both and WAP will even let you have specific Knightly Orders like Knights of the Blazing Suns and Knights Panthers.