I kind of imagined 14 becoming part of 15 when the former is at the end of his life. That’s why 15 already had three for all of the trauma. Maybe the Watcher from Logopolis was a bi-generation like event.
It’s not a bad season and Mel is over of my favourite Classic Who companions. And I liked all the Valeyard name jokes.
While I know it wasn’t meant to be funny, the final scene of the Doctor exercising and then having regenerated in the first scene of the next season really looks like he died from exercising and healthy eating. They even make fun of that in the series 8 intro with the Pater Noster Gang.