This is how I would write a Iron Fist movie. First, I would merge Danny's character and his father's Wendell. Orson would be his biological father.
This would have a Indiana Jones/ Kung Fu vibe.
Orson Rand is a 26 year old alcoholic whom loves going on archaeology adventures with his team of treasure hunter and bandit wearing a yellow mask during his travels. He grew up in Ku'n Lun where His family was stranded and he became their best Iron Fist at age 17, naturally having a genius level talent for fighting. Shortly after becoming the Iron Fist he became bored and left instead of preparing for the 7 city tournament which would come in 10 years time. Little did Orson know that he left behind a son in Ku'n Lun named Danny Wendell Rand.
At the beginning of the Iron Fist movie, Danny, the opposite of his father Orson, is the worst martial artist at Ku'n Lun, being overshadowed by all in his class, especially Davos, his adopted father's son the Thunderer. He also has asthma which he inherited from his mother who is sick and dying. Because of his upbringing, he is kind hearted and responsible not like his father Orson. At 9 years old, he sets a plan to escape Ku'n Lun when the city's gates connect to Earth and find his irresponsible father Orson and bring him back to Ku'n Lun one last time so Orson can see his mother before she passes away and so Orson can prepare for the upcoming 7 city tournament where the winner gets their city wealthy and rich. Little does Danny know that from the 8th secret city the Iron Fist killer follows him.
Danny finds Orson, bonds with him unwillingly and goes with Orson on his last treasure hunt before they go back to Ku'n Lun. But Orson soon discovers that with the presence of the Iron Fist killer, and without completing his Iron Fist training he begins to lose his IF powers.
The movie would end with Danny and Orson in a final confrontation with the Iron Fist killer at the gates of Ku'n Lun before they close off. Orson protects Danny and fights tie Iron Fist killer to a stand only to be losing until the gate closes causing Orson and the Iron Fist killer to be stuck inter dimensionally. The last scene he sees is a bloodied passed out Orson being held while pointing at the Thunderer declaring that he will be back when the gates reconnect in 10 years and that he will murder the next Iron Fist. Danny is heart broken but at the end of the movie he looks upon the Iron Fist crest and declares that he will become the next Iron Fist and kill the Iron Fist killer.
Iron Fist 2:
Iron Fist two would have a teenage Danny Wendell Rand train in Ku'n Lun for the big tournament for the next Iron Fist to come. He has trained hard for the last 7 years and is now 17, around the same age as his father when he became the Iron Fist. He is not like his father, who is still a martial arts genius but he has more drive and responsibility than his father training hard enough to defeat Davos. In the middle of the movie he will fight Davos and make a mortal enemy out of him (Davos leaves to the serpent city after this) and battles the Dragon to become the immortal Iron Fist. But he is not alone when he confronts and outsmarts the Dragon, it turns out the Iron Fist killer is at large and decides to steal the Dragon's soul before Danny could conquer it for himself. Orson would turn out to still be alive, fight the Iron Fist killer and get killed. He would tell Danny to plunge his fist into his chest and collect whatever power Orson has left and whatever the Iron Fist killer has not stolen already.
Danny, although only having a small portion of the Iron Fist powers and still overshadowed by his father. His Asthma is also cured thankfully. He is enraged and fights the Iron Fist killer, discovering that his handicap of not having the full Iron Fist power is to his advantage as the Iron Fist killer is only truly strong against another immortal weapon. Instead of being powered by the Dragon's power, it is his rage that he collects in his fist that allows him to defeat the Iron Fist killer.
With his satisfying victory, he plunges his fist into the Iron Fist killer becoming the most powerful Iron Fist with the Dragon's powers and a small portion of Orson's powers in his fist as well.
The Thunderer is not only proud but excited that Danny has become so strong. Even though Danny lacks the experience that his father did, he has much greater amount of power. They now have a Iron Fist to compete in the 7 city tournament.
In the end it will be revealed that Yu-Ti was working with the Iron Fist killer the whole time trying to steal Orson's family inheritance so he can live a rich and wealthy life outside of Ku'n Lun. In return he would sacrifice his city along with all the other cities to the 8th city full of demons.
Iron Fist 3:
The third Iron Fist movie would be about the 7 city tournament, Danny, Thunderer and Davos rebonding, Yu-Ti's plot, the Immortal weapons getting kidnapped and escaping the 8 cities and a final confrontation would be between Yu-Ti who has found a way to steal a portion of all of the Immortal Weapon's powers defeating them all and Danny beating him 1 on 1 with Davos helping as a distraction.
The end would have Danny to try and live on Earth, inheriting Orson's fortunes and finally Luke Cage would make a cameo confronting Danny about needing a partner on a case setting up a possible heroes for hire.