Battle Armor
A interesting ability, it helps with crits but is that such an issue?
I don't know about everyone else, but I get hit with at least 2 criticals a game. Usually at the most inopportune moments.
Solar Power
My favorite this thing has a low enough sp. attack for it not to be broken (using sunny day is the same as a growth boost that only lasts 5 turns) it fits the art well enough to work (imagine this thing drawing power from)
Wouldn't this + sunny day = 75% special attack increase on fire moves? Or does Sunny Day count like a stat up, effectively making it +100% special attack on fire moves? Plus, with the one item sunny day can last 8 turns. Add a life orb or choice specs/scarf and this thing would be beyond powerful.
Flash Fire
I don't see why this would be broken, it fits the art well enough and would be nice.
Of the three groupings of counters, one is fire Pokemon for the shear fact that it resists both STABs, and then hits back neutral with STAB. Flash Fire would negate this counter grouping.
Rock Head
hmmmm.... it would make the odd CB sets almost usable but i dont realy like it, its wood not rock.
Steelix has it, and he's metal not rock. Sudowoodo has it, and he's wood not rock. Marowak has it, and she's bone not rock.
Isn't there an ability that gradually heals HP in the sunlight? I'm sure there is, but I forgot the name. It would be just like Ice Body or Rain Dish.
We can call it Synthesize, Recharge, or Sol Heal.
Going off a list of abilities:
Battle Armor
Flame Body
Inner Focus
Pressure
Rock Head
Sniper
These are the only things I can really see fitting this guy without being overpowered or stupid weak. Two are offensive (Rock Head, Sniper), one is neutral (Pressure), and three are defensive (Battle Armor, Flame Body, and Inner Focus).
It should have one defensive ability and one offensive ability, likely with Pressure falling more in line under defensive abilities than offensive. All of these are fine choices, though a couple do stand out.