I think it's a brilliant idea. To show what a good idea i think it is here are some suggestions
Of course feel free to pick, choose and ignore anything that you want, you are the person doing the work after all.
Iconic Dragons
St. George’s Dragon.
Emphasis on physical capabilities probably. I live within ten miles of the spot where the fight supposedly took place and the hill of the battle is called ‘dragon hill’. The top is completely devoid of vegetation because; the story goes, of the dragon’s poisonous blood so that could be worked in.
Other Suggestions of Iconic Dragons
Jorgamund, The Midgard Serpent (linnorm/wurm form)
I know a version of this was done for the linnorms in second edition but I don’t think any such thing exists for third. This was the dragon child of Loki destined to kill and be killed by Thor, it was supposed to have venomous breath and be so large that not even Thor could lift it. The jorgamund serpent lives in the oceans, dormant, with its tail in its mouth and was said to form the sea. Massive water or weather control abilities might be the way to go if you choose this.
The Lambton Worm (linnorm/worm form)
Is an aquatic and seemingly not hugely intelligent creature from Britain. It was said to be large enough to wrap around a hill nine times. If it was cut in half the pieces were said to join back together leaving the creature unharmed. The only way the creature was finally beaten was by a holy knight wearing armour covered in long spikes.
Nidhogg
If you wanted to go truly epic on the levels of Asmodeous/The Adversary etc. then you could try to do Nidhogg the world serpent. It is the embodiment of entropy/destruction/annihilation and is forever gnawing at Yggdrasil the World Ash, which supports all creation. This would probably require divine ranks and Epic rules
The Firedrake
Is the creature that killed Beowulf of Grendle-smashing fame. It is your typical treasure hoarding, firebreathing dragon so there might not be any reason to do it on top of a creature such as Smaug or Fafnir (for example).
Smaug
Is probably where dragons come closest to their dungeons and dragons counterpart but he truly is an iconic and famous creature. I think it would be fun to do
Dewi, The Red Dragon God of Wales
(Hard to find information on this one so pardon any gaps etc.

) Dewi was an ancient Welsh/Celtic god-like being who was said to take the form of a red dragon, this is the creature that features on the welsh flag today. I think this would probably be one of the better opportunities to do an iconic dragon as a magical, mystic, hugely intelligent creature (not necessarily evil).
The Tarasque
You could try reclaiming this creature if you wanted

, it was originally a dragon that was the daughter of leviathan and thus a water creature, her mother was the gigantic snake onachus.
Tarasque resembled half land animal, half fish. She was bigger than twelve elephants, had teeth like ivory swords and skin like iron. . This bizarre dragoness stood on six mighty legs each equipped with the murderous paws of a giant bear. She had the head of a lion with a large golden mane. A massive carapace encrusted her back resembling the shell of a giant tortoise, bristled with an armoury of mighty spikes her long serpentine tail ended in a barb as sharp as a spear's point. And, of course, and her breath was flames.
You could edit out the slightly mammalian bits if you didn’t like them

. At one point the people in the part of France she was terrorising tried to lure her into an evil swamp to drown her but as the swamp was a place of the devil and she was a creature of the devil she was forewarned.
The creature was eventually overcome by St. Martha who subdued it with holy water and a cross. She also sang hymns and her victory has been put down to either of these things. Either that the creature was compelled by her faith or it was entranced by music. After this it obeyed her utterly, allowing itself to be leashed etc.
Quetzacoatl
This could be included in your iconic dragons if you felt that the current coatl didn’t quite fit the bill. This was the winged serpent god of the morning star and was a bringer of life, fertility and rebirth, he commonly adopted the guise of a young man in a feathered cloak or an old man with a broken walking stick.
Ladon, The Guardian of the tree with the golden apples, The dragon of Evening
One of the twelve Labours of Hercules was to steal the golden apples of the Hesperides. The Hesperides (3 maidens) owning the tree had it guarded by a hundred headed never-sleeping dragon called Ladon that was able to talk in a multitude of languages and voices from it’s various heads.
The Dragon of Colchis
Was the guardian of the Golden Fleece sought by the argonauts, it was put to sleep by the drugs or spells of Medae. It had poison fangs
Fei Lin, The Dragon of the winds
Was an oriental (Chinese) celestial dragon that held all of the winds in a sack, he was no bigger than a tiger but was hugely powerful. He was said to have a bird like head with horns and a tail like a snake. He was a troublemaker that could move with unbelievable quickness.
You may also want to look at this page:
HERE BE DRAGONS