Homebrew Hero

OK, I got to thinking about our current 'challenge monkey,' Bragg, and how horrid he is in an actual challenges. And so, I thought I'd present a homebrew replacement. Meet:

Denali, the Mountain
Bruiser statline, with +2WS, +1W, +1I, and +1A (from equipment)
Heavy armor and two enchanted Ironfists (4+ armor, 6+ parry, magical weapons)
Canny Pit Fighter: Must always challenge in combat, or accept challenges. While in a challenge, combat always happens simultaneously.
Tougher Than Nails: Immune to Heroic Killing Blow and Multiple Wounds rules; only takes 1 wound on a successful hit.
Roar of the Crowd: Gains +1 Attack for each rank bonus of the unit he's in (to the standard rank bonus.)
Adoring Fans: Gains +1 Ld for each rank bonus of the unit he's in (to the standard bonus.) If the unit is a horde, he gains Stubborn.
Finishing Flourish: After defeating an opponent in a challenge, Denali can trade Overkill points for healing, up to his maximum starting value. Remaining Overkill points are then doubled for combat resolution.

Just something quick and dirty I threw together. Figured a veteran pit fighter would be a better challenger killer than our current Gutsman. Quick glance, I'd price him at around 210-220 points (8th Ed)

Any thoughts or suggestions would be appreciated.

I think he has a lot of special rules, more than a lot of characters, they are good rules don't get me wrong, but I think an, as you say, 'challenge monkey' is served better by being kept simple.

-The stat-line seems good, I would perhaps be tempted to keep his wounds the same as a bruisers though.
-I like the idea of having two iron fists, and it fits thematically, I feel as magic weapons they should probably provide some sort of actual, discrete, bonus though.  Perhaps a 4+ parry save (basically a worse ward save I guess), or re-rolls of 1s on To Hit and Save?

-Canny Pit Fighter:  This rule is good, the wording should probably be something like, "When Denali is engaged in a challenge both he and his opponent strike simultaneously, regardless of relative initiative values or any other effects." to avoid confusion. 
-Tougher than Nails:  I would probably remove this completely; Heroic Killing Blow is rare and unreliable, if you want some protection from multiple wounds then perhaps he could halve them like the Stonehorn? 
-Roar of the Crowd:  Cool rule, I like it and see nothing wrong with it.
-Adoring Fans:  I'd probably just remove this rule as well; it adds extra bloat for little reason, if he's in a horde he gets the benefits of such anyway, and letting him gets stubborn is kind of like providing a free Crown of Command, seems like a bad idea balance-wise.
-Finishing Flourish: I would say provide either the healing or the doubled overkill bonus, not both and the latter seems more appropriate.  If you are intent on keeping the healing then it should probably provide only 1 wound per combat round at max.

Yeesh, this fella needs 2 pages to himself! The idea of a pit fighter is quite cool, and really thematic. Would have been awesome to model too.
Right, down to business:
Denali, the Mountain: 190 points
M. Ws. Bs. S. T. W. I. A. Ld. Sv.
6    5    2   5  6  5   5  5  8    4+
Equipment: Denali fights with a pair of Ironfists, soaked in the blood of many fallen champions. His brawling blows are so furious, that when Denali is fighting an enemy character, or Independant Character in a challenge, Denali may re-roll 1's to hit with the Ironfists.
Mountain Man Chains: These chains were often used to ensuring the pit fighters of Mourn would not start the fight before the Tyrant declared it. With skull-clattering blows, the chains often snap, releasing Denali's unbridled savagery. For every To Wound roll of a natural 6, a portion of Denali's chains snap, healing 1 Wound. Denali cannot gain more wounds than he started out with.
Heavy Armour.

Special Rules: Fear, Ogre Charge
Canny Pit Fighter: The rough-housing attacks of Denali may substitute his Inniative for that of his opponent's in a challenge.
Roar of the Crowd: Denali is a glory-hogging fighter, always aiming to win, and please the crowd whilst doing so. Denali receives +1 Attack at the beginning of the Combat phase, euqivalent to the Rank Bonus of the unit he is joined with.
Showboat Kill: Whenever Denali slays his opponent in a challenge, Overkill wounds are doubled for the purposes of determining combat resolution.

That seems a bit, fairer. He's 190 points because he is only S5 and has no way of ounching through Armour or really high T.