Paladins are supposed to be natural leaders, but their party buffing skills are rather underdeveloped. They're a melee class with self-healing, but they're extremely one-dimensional, and except for their Saves, pretty much inferior to other classes at any one aspect of the game. Plus, they only have two current Enhancement trees. I think a third tree could be added to add a little diversity and dimension to the Paladin's playstyle, while keeping within their core focus:
Core abilities: Your Aura extends an additional 5m (2m?) for every Core skill you possess
Core Skill 1: Your Aura now grants Deathward to everyone within it.
Core skills 2-4: Your Aura now adds an Aura bonus to Concealment/Attack Speed/Incorp/Dodge equal to 1/2 your CHA modifier
Capstone: +2 Cha, all party members are always considered within your Aura while in the same zone, bonus increased to 3/4 your CHA modifier
Line 1: Herald. Summon a divine Herald of your deity; basically a Paladin copy of Skelly's PM.
Line 2: Adds Blur/Haste/Displacement/GH to your spellbook as L1/2/3/4 spells (not SLAs)...or other possible Divine buffs instead that aren't already in the Pally spellbook.
Line 3 and 4: AB: Inflame (same as Warpriest), Cha/Con multi-selector, maybe Efficient Metamagic: Extend and Emp Heal
Line 5: A +1[W] melee attack that grants stacking bonuses to allies within your Aura when it lands: +damage/USP, HOTs, elemental absorbtion, threat reduction, etc., with additional benefits being added with additional investment in the line.
L5 skills: GH (Line 2), grants your Herald CCW (CSW?), Lesser Restoration, and Raise Dead (Line 1), adds Immunity to Stun/Daze/(Paral?/Hold?/Etc.) to your Line 5 special attack (Line 5).
Basically the idea is to make heavily-invested Paladins extremely desirable in group settings, granting significant bonuses to nearby allies and gaining useful buffing skills and spells, while the Herald makes the line also worthwhile for solo play and not simply a buffbot. While it doesn't directly increase the Paladin's tankability or DPS the way SD or KotC does, the more allies in your group, the more meaningful the paladin's bonuses become.
Everything here is negotiable too, if a given value or choice seems overpowered - its the basic idea and mechanics of the tree (buffing auras, Herald pet, boosts to allies) that's the main suggestion.