Building a Dragonborn Con/Cha Paladin - any advice?

[Fortuna]

Some interesting advice all around.

Virtuous Strike + Power of the Sun is extremely tempting. Handing out radiant vulnerability while wielding a sunblade is a thing to which I have trouble saying no, particularly when we also have a cleric in the party.

I'm not massively worried about wisdom, but I suppose it won't hurt me to lose a bit of charisma. That makes Io's Challenge even more tempting, of course.

I think I really do like Ardent Strike for my second at-will. I'm reasonably confident that my existing mark punishment is a good enough deterrent for the time being, so spreading the marks around is a good next step.

In terms of my next feat: the choices seem now to have expanded to Power of the Sun, Bolstering Breath, Io's Challenge or Devout Protector Expertise (Dragonmark feats are not on the table, I fear). While I would love to have all of them, obviously I can't yet. Bolstering Breath appeals because it changes how I use my dragon breath - instead of needing to work around allies, I suddenly want to catch allies in it. DPE is somewhat less desirable than it might be, since as I recall two of the other three party members already have a shield bonus to AC, so that the extra benefit is essentially "The ranger gets a +1 shield bonus to AC". At that point I could just take Heavy Blade Expertise instead and get as much or more out of it, since I have no great desire to take any implement powers anytime soon, and if I ever did want to I could retrain. Power of the Sun is awesome indeed, although I suspect my DM would swear the sky blue in response. And, of course, Io's Challenge gives a nice bit of bite to my DC while I'm bloodied. This is where I really feel I need advice, and I'd be grateful for anyone comparing the benefits of these feats.