That could work. I had another proposal upthread for your consideration, but I'm not tied to it. Which do you prefer?
That would work for me. I think I like that route better than the additional damage from spells in favored enemy.
Anti-Dragon Casting (Ex): Undead dragon slayers gain a bonus equal to half their favored enemy bonus on caster level checks to overcome the spell resistance of dragons (this does not stack with other bonuses, such as from Spell Penetration) as well as the effects of Spell Focus for all spells cast against dragons. At caster level 17th, an undead dragon slayer also gains the effects of Greater Spell Focus for all spells cast against dragons. In addition, an undead dragon slayer may Maximize one spell per day at no cost if that spell's target is a dragon.
I'd rather cut out the free Maximize Spell. The DC and SR penetration seem enough for the basic ability. We could give them free Metamagic feats as one of their "optional picks" special abilities.
Good plan.
Before starting on the menu items, we had a few that we thought might be good for all undead dragon slayers, like weapon throwing. Which of those do we want to forget or promote to all the undead dragon slayers? I'm starting to think we might have just about enough for all of them, though I have some inclination to give all of them a dodge bonus against dragons (I had that listed as Dodge to AC, save bonus, attack bonus*).
Before starting on the menu items, we had a few that we thought might be good for all undead dragon slayers, like weapon throwing. Which of those do we want to forget or promote to all the undead dragon slayers? I'm starting to think we might have just about enough for all of them, though I have some inclination to give all of them a dodge bonus against dragons (I had that listed as Dodge to AC, save bonus, attack bonus*).
Yes, some increased defenses vs dragons makes good sense.
I'm not sure about the weapon throwing. Unless it gets free weapon returning as well it's just a fast way for the Slayer to disarm itself. Still, if it's pretty useless I suppose that means it doesn't increase its power much to make it a general ability.