So reviewing Bloodlines as one of my players expressed interest, I thought again of their relationship to Birthright Bloodlines and my thought of rewriting those to the UA format.
That made me think of just making "Blood of Kings" generic bloodline.
And then out of nowhere I thought about Dragonmarks.
Thus:
Blood of Kings
1st Diplomacy +2
2nd Favored
3rd Charisma +1
4th Leadership
5th Subject Affinity +2
6th Guildmaster**
7th Sense Motive +2
8th Landlord**
9th Wisdom +1
10th Rulership**
11th Subject Affinity +4
12th (Epic) Leadership*
13th Bluff +2
14th Extra Followers
15th Intelligence +1
16th Improved Cohort
17th Subject Affinity +6
18th Legendary Commander*
19th Intimidate +2
20th Mind Blank 1/day ***
Subject Affinity: The affinity skill bonus for those with the Blood of Kings applies to anyone they are in charge of, starting with their followers, and continuing with any subjects they rule over.
* Powers of Faerun allows for Leadership scores above 25 (essentially, Epic Leadership), as the default. This uses that and grants Epic Leadership and Legendary Commander as bonus feats.
** Guildmaster (DMG II), Landlord (SBG), and Rulership (PF) all assume some use of additional optional rules from those books. If you do not want to incorporate those rules, consider replacing these with other Leadership based feats. Wild Cohort, Dragon Cohort, Undead Cohort would be prime options.
*** Other capstones in the book are immunity to an energy type or DR. This is effectively immunity mind-affecting spells. I figured it was reasonable for a king.
Dragonmark Bloodline
1st (mark skill) +2
2nd Least Dragonmark
3rd Charisma +1
4th Dragonmark Prodigy
5th Dragonmark Affinity +2
6th Lesser Dragonmark
7th (mark skill) +2
8th Dragonmark Adept
9th Strength or Dexterity +1
10th Greater Dragonmark
11th Dragonmark Affinity +4
12th Dragonmark Visionary
13th (mark skill) +2
14th Siberys Mark
15th Intelligence or Wisdom +1
16th Least Dragonmark Mastery*
17th Dragonmark Affinity +6
18th Lesser Dragonmark Mastery*
19th (mark skill) +2
20th Greater Dragonmark Mastery*
Dragonmark Affinity: The bonus applies to people with the same Dragonmark/members of the same Dragonmarked House.
Skills: Are by dragonmark;
Mark of Detection: Spot/Diplomacy/Listen/Sense Motive
Mark of Finding: Search/Intimidate/Knowledge (nature)/Survival
Mark of Handling: Handle Animal/Heal/Ride/Survival
Mark of Healing: Healing/Knowledge (nature)/Sense Motive/Diplomacy
Mark of Hospitality: Diplomacy/Knowledge (local)/Sense Motive/Diplomacy
Mark of Making: Craft/Knowledge (local)/Appraise/Diplomacy
Mark of Passage: Diplomacy/Knowledge (local)/Bluff/Ride
Mark of Scribing: Decipher Script/Speak Language/Profession/Forgery
Mark of Sentinel: Sense Motive/Intimidate/Handle Animal/Ride
Mark of Shadow: Gather Information/Disguise/Move Silently/Listen
Mark of Storm: Balance/Knowledge (geography)/Climb/Swim
Mark of Warding: Search/Knowledge (a&e)/Disable Device/Craft
Ability boost: Should be variable by Dragonmark. The table has generic choices.
* Least/Lesser/Greater Dragonmark Mastery are as per the Dragonmark Heir prestige class.
They essentially get all the dragonmark benefits of the Dragonmark Heir and Heir of Siberys prestige classes except for the bonus action points.
The highest level benefits are not particularly spectacular, but the alternative would be losing them completely or delaying the Siberys Mark until 20th level, and that didn't seem useful.
Also, they don't get the CL increases. These could still be gained from the various prestige classes available for the marks, but should probably be given as a gratuitous bonus tagged into some of the feats.