I just read and liked:
Falling Into Place by riftintime
A very nice AU Just a nice read. When this begins, Jack is with Gwen, but it's not what you think, so keep reading.
https://www.fanfiction.net/s/6750092/1/ When the Stars Turn Blue, also by riftintime
Another AU, this one was a real up-all-night, couldn't put it down, page-turner. Very interesting premise, very well done, I thought. This was a second read, but I'd forgotten what happened and had to keep reading to the end. :)
https://www.fanfiction.net/s/7095796/1/ I should do this more often.