Interesting thoughts. But one thing would change drastically from the Doctor meeting Jackie first; he'd learn to respect her much sooner. Which would mean he might not let Rose go with him unless a few things changed. If Jackie became his friend, I don't see him letting his friends be insulted or disrespected. Especially as Nine. (My two cents.)

Sylvia... Yeah. She also might've forced a different end to Journey's End had she known him before. I mean, can you imagine a phone call from Donna, checking in on them, and them learning about the Meta-Crisis Doctor? They'd want to meet him, for sure.

I might have to write something like this one day. Just as I might, as a lark, write a sort-of self-insert story that's been fluttering around in the back of my mind for a while. (Ever had the thought of 'what if you found yourself inside a favorite story and tried to change things'? Well, I thought it might deal with issues of time-lines and consequences.)