Actually the most important thing is that he keeps his baker quote on at least his baker skin XD.
As for design, we know that the previous Pantheon (the one Aurelion Sol killed) also shared a similar design as described in the current Pantheon's lore, so I think this is the direction Riot wants to go with him.
Then, I see her. This world’s imbued warrior is alone at the peak of one of the smaller summits, brandishing a starstone spear. She watches me through a veil of annexed flesh, a mere spark masquerading as lightning. A thick braid of auburn hair is draped over her shoulder, falling over a golden breastplate that covers pale, freckled skin. Her eyes, the only bit of her face not shielded by a battle-worn helmet, flash a jarring shade of red.
She calls herself Pantheon—the warring fury of Targon incarnate. She is not the first of this world to wear the Pantheon mantle. Nor will she be the last.
Her glittering cape flaps out behind her as she raises her muscled arm and makes a motion like she’s pulling on a great chain. The tug on my crudely enchanted tether wrenches me off course, toward the mountain upon which she stands. And she’s yelling at me.
It can still be improved on without changing the silhouette however, "bedecked in archaic armor" can mean almost anything in terms of design.
Looking at the region, we know that it snows on Mount Targon and thus you could incorporate certain gear to provide warmth for your warriors, but do Panth, and Leona even feel cold?? Also, in Leona's lore we are told that she got her armor from Targon, and thus wouldn't it have some sort of 'celestial' design (Demacia and Noxus have their own design for the 'shape' of their armor and 'flow' of their architecture, likely Targon would also share this). But currently the armor varies very widely between the aspects,
looks like a knight and
closer to a centurion. As for what the armor is made of, we can assume it would be made of Star gems/ star stone like
's coronet or Pantheon's spear respectively.
Also Taric has some strange 'rune??' on his arm, would this also be the case with the other aspects, Leona is known for her shine as though she were a living sun, could this actually be a 'full body rune' and where would Pantheon's rune reside maybe on his shoulder as to dodge similarity with Taric but still hint at that fact that his power is in his martial prowess, obviously Diana would have her's on her forehead. once again beyond this, we don't even know the significance of this 'rune??' whether it is a manifestation of their power or a brand of some kind (to show "hey look at this I'm an Aspect").