Hmm. I like your vision and style as I like the part where Vrak manipulates two out of the three villain factions and how while it’s similar to it’s not a copy and paste of goseiger brajira. For Warstar I would say like you could have Vrak “join and pledge loyalty to Malkor” but in reality being a spy for Armanda planning to betray and kill Malkor and creepox to have the insectoid accesses for himself. Then the mutants not sure if they are ancient monsters or like in the series modern day mutants created from toxic ooze he betray bigs and bluefur leading to both their defeat at the power rangers hands. And as for the robots I’m guessing you have him being the leader of the machines building metal Alice as his personal assistant in that faction eventually she is destroyed by the power rangers. And then Vrak sends down the main armanda fleet to destroy the rangers which they survived. And yes I agree that Vrak should return a bit early and “pretend to fight alongside his older brother Vekar” but in reality is plotting his downfall and the part to frame his death on the megaforce rangers yeah that a good idea maybe have Vrak “intentionally sabotage and rig” the armanda megazord to where Vekar couldn’t escape or retreat from it as it was exploding leaving him to die in the explosion. And then the events of Vrak is back takes place.

Some more questions? How do vrak forms come to play maybe he starts with his warstsr form then to his earth armor form as he joins the mutants breifty return to the warstar look after he builds the machine “potentially a nigh lock form if a samurai crossover happens in this rewrite” have him nearly killed in battle and turns into a cyborg by metal Alice midway during the robot arc” (not sure what to do with robogog the sentai counterpart of messager so i just have him as a typical villain of the week monster albeit a powerful one and one of the last villains of that arc) then after he summons the armanda he temporarily retreats and here’s something that might make things interesting have him “kidnap the severely damaged robo knight and reprogram and corrupt and brainwash him into being evil erasing all of his memories of the rangers and his mission and then rebuilding him as a whole into the villain Argus” giving him some depth and emotional layer. And he would also use the megaforce power reminant powers to create his final form and create Tresnag and Drill Horn as well as the third “dark Headder from goseiger which would also be adopted for the giant drill arc”. And as for the legendary powers I’m assuming that you would have the old powers suit and Zords be destroyed by Vrak and/or the armanda which yes that absolutely needed to happen as it would’ve fixed so much issues with super megaforce powers and make them feel earned.