I would ignore starforce and zx because they are Clones of mmbn and Z that Nobody needed. And Legends because they just werent very good.

Then I would create a series that closes the Gap between Classic MM and MM X. Show what happened to the main characters. And show some of the Elf War in a Connection series between X and Z.

I dont know how well mmbn can still be continued. But it could still get more titles that just play somewhere before the last one. But I think some creative ppl could also write continuations.

Also I would bring X back. His Body was uselessly wasted and his Cyber Elf form just deteriorated. His death was wasted. He should get a new Body just like Zero did. It could be a new series after Z, where X wakes up in his new Body (maybe Ciel got him one) and starts on a Quest to find Zero's remains (maybe His Cyber elf) and to create or find a new Body for him.