Your ideas sound good for the most part. However, I don’t know how about having a fully trained Jedi Knight running alongside Luke. Ren wasn’t a fully trained darksider when he wiped out Luke’s disciples, which works in they were still just fledglings themselves. But Ren being able to take on and defeat a Jedi who completed their training when he couldn’t beat the untrained Rey years later? That sounds problematic.
Well, there has been no official statement saying that none of Luke’s pupils became Jedi Knights, so I just went with that (plus, I wanted to get a Tales of the Jedi reference in somehow with Vima). But I do see your point. If necessary, Vima, my Jedi character, could be a former Jedi who left Luke’s Academy after a tragic accident happened. Still, we’ll just have to wait and see what the Disney canon will come up with.