Thanks to everyone who commented with topic ideas! It'll take a bit to go through everyone's, which is great!
The first topic suggested was by
who_in_whoville and is about Ten II:
Can Cloen feel Ten, or at least sense him somehow? And if so, what happened when Ten regenerated into Eleven? Was the link broken?
And I would add as a question, if there was a link would he tell Rose about it? Or would he want to keep Rose from thinking about the other Doctor as much as possible?