[chrispedersen]

Hmm... it wouldn't be that hard to make a table that said
this leader can lead the following troops.

Actually gandalf, edi's database already does this.
It tells you if troop is demon, undead or magical.
So, all you would have to do is a pretty simple case.

Check each troop type vs the table.
If troop 1 or troop2 or troop three = magic, include 1-2 std magic leaders.

If troop 1 or troop2 or troop 3 = undead, include 1-2 std undead leaders

same for demons...

Now, more spiffy would be to use tailored leaders and troops.
But also more work.