1) Dragon

The might of the dragons are known throughout the land. This scaly terror of the skies feels no mercy and nothing will escape the fiery splashes of his breath. We already have the Baby Dragon (currently exclusive to Clash Royale). Why not give the big one just like Mini P.E.K.K.A to P.E.K.K.A. The Dragon can be a tank just like the Balloon with higher HP. It should have slow speed and deployment time should be around 5 seconds. Of course, it is quite overpowered so it has to have the Legendary rarity and he requires 8 elixirs to deploy. It should be unlockable in Royal Arena.

2) Healer

This majestic creature lives to protect and aid her fellow troops. Any army is improved with her healing support, but make sure to protect her from air defenses! Clash Royale does not have anything about healing troops. Healer from Clash of Clans may be seen as an overpowered card if she ever transitions to Clash Royale.
She should be an EPIC that requires 4-5 elixirs and is unlockable in Arena 5 (Spell Valley). She can heal within the radius of 3-4 like the Baby Dragon. She should have HP around the same as Princess. She cannot attack any units, just like her counterpart.

3) Bowler

This big blue dude digs the simple things in life - Dark Elixir drinks and throwing rocks. His massive boulders bounce off their targets and hit again behind it for double strike!  The Bowler will be the answer for spammers and hut users in the game. Like in Clash of Clans, his attacks will bounce off twice. He should be like a moving mortar just like the Princess to the X-bow (because of her Long Range). His range should also be as far as the Mortar's range.
He should be unlockable in Arena 4 as a Legendary rarity. His HP and area damage should be a little bit higher than the Princess.

4) Barbarian King

The Barbarian King is the toughest and meanest Barbarian in all the realm, whose appetite for Dark Elixir has caused him to grow to a giant size. He can attack enemy villages or guard your village.  Barbarian King, if he ever transitions from Clash of Clans, will be a very good legendary card for Arena 3. He would cost 10 elixirs as he can act like a Witch, which summons one Barbarian every 10 seconds. His HP and Damage should be around the same as P.E.K.K.A.

5) Archer Queen

The Archer Queen is an eagle-eyed warrior, whose weapon of choice is a modified X-Bow that few men could dream of wielding. She can attack enemy villages or guard your village.
 Archer Queen will be a great legendary card for Arena 7. She should require 7 elixirs. Same range as the Musketeer or Royal Giant. Her HP should be quite below the Hog Rider, but her hit speed should be as fast as the archers and he attacks anything.

6) Grand Warden

The Grand Warden is a brilliant tactician who has spent years learning to harness powerful artifacts of unknown origin. He toughens troops that attack enemy villages or guard your village.  Grand Warden will be a great legendary card for Clash Royale Arena 5, Spell Valley. He should require 6-7 elixirs to deploy. He can act like a healer but less radius, while being a ranged unit. His attack will be AOE damage, and his damage should be a little bit stronger than the Ice Wizard.

7) Earthquake Spell

Weaken Walls and buildings with crippling earthquakes! Earthquake Spells damage structures based on their maximum hitpoints. Repeated Earthquakes deal decreasing damage to the same buildings, but increasing damage to the same Walls. No wall can withstand the might of four Earthquake Spells! Earthquake is a unique spell in Clash of Clans. It takes off percentage instead of having a specific damage in an area. In Clash Royale, it would be a great spell card with a common rarity. Its elixir requirement should be around 2. It would be a good way to deal damage with a tower or any defensive building who has a high HP since higher HP means higher damage.

8) Air Defense

This anti-air tower is deadly against flying enemies, but can't target foes on the ground. Place it wisely to cover as much airspace as possible.  It is actually about time to have a pretty decent air defensive building. Although this may come off as an overpowered building since most air units have low HP. It should have 3 elixirs and unlockable in Arena 3. The card rarity should be common, just like the Cannon. Actually, its stats should be based on the Cannon itself. However, it should be slightly lower damage and a little bit higher health.

9) Eagle Artillery

The Eagle Artillery has nearly unlimited range and targets tough enemies with exploding shells. However, it won't activate until a large amount of troops have been deployed.  Eagle Artillery covers almost all the area in Clash of Clans. However, in Clash Royale, it will be significantly overpowered. What if it is an EPIC card that requires 8 elixirs and unlockable in Arena 6? It should have a range of 13 so you cannot put it behind the tower and easily win games.
It needs 15 seconds to deploy,  6 seconds hit speed, and has 40 seconds life span. Fair enough? It should also attack the same way it attacks in Clash of Clans. It is going to look for the highest health in each of its attack since it recalculates each time.