Well…
Team Avatar was going to investigate the seemingly nefarious beverage company. Asami would be pretend to be a business partner inspecting the facilities with her two body guards (Mako and Bolin). Simultaneously, Korra, Opal, Kai and Jinora would break in and investigate themselves. I wanted to continue the tension and frustration between Jinora and Kai to try and mature and add nuisance to their relationship.
The team would naturally capture the suspicious CEO only to discover he had nothing to do with it. Equalist operatives attack, leaving Jinora still paralysed with her PTSD as the battle rages. Kai would be placed into a situation where he would fall into a vat of liquid. Jinora confronts her fears and dives in to save him. There would be a nice moment, despite the Equalists escaping.
Team Avatar would take the samples back to Zaofu to analyse the poison but it is a laborious an essential task. Despite being offered to come along, Kai does the mature thing that Jinora wanted and stays at Zaofu analysing the toxin with Opal and Su. I wanted him to learn patience and show his determination to grow into a better person for his soulmate.
Team Avatar would find the Equalist stronghold in the swampy jungles, narrowly missing the Commandant (who was escaping by airship) who was taking litres of the anti-bending poison to contaminate the reservoir to Omashu.
Epic rooftop fight with Jinora beating the Commandant and cool speeches. Everyone meets back up in Republic city and Kai begins trials for getting his stripes.
Epilogue consists of the future where Jinora and Kai are old and happy.
That's was basically what I had planned.
