I wonder if the real reason for Sophie appearing on the update today is down to the desire to have a senior presenter in the building for as much as the day as possible in case of changes in the Boris situation. There is little point in having Sophie present this update early in the week if it means a less experienced presenter ends up reading the six and ten towards the end of the week.
You could be right. Or maybe Clive or Reeta will do the Six and Ten towards the end of the week, but need a couple of days off since they both presented Monday and Tuesday.
I'm pretty sure Sophie would have done the News at One instead if they wanted someone 'senior' in the building this morning, and Jane would have done the Special.
Hwu, Kate, Sophie and Mishal all have at some point presented rolling news on BBC News Channel and/or BBC World News.
Mishal was the main overnight presenter before joining Breakfast and is still an occasional relief presenter for BBC World News. She has also done stints in Washington and Singapore as a presenter.
Hwu presents an hour of news at 5pm, Kate and Sophie started as a news channel presenter, and Kate is still an occasional relief presenter for BBC News Channel and BBC World News
Mishal started out on World Business Report in about 2001, give or take, before taking over the 2000-0100 GMT shift when it was vacated by Philip Hayton. She didn't do overnights, per se - they were presented by Clarence Mitchell, Rageh Omaar, Heather McCarthy, Martine Croxall, Susan Osman, Deborah MacKenzie and Alastair Yates around that time. Mishal pretty quickly moved to Washington in around about late 2002 to launch the first Washington/London newscast with Adrian Finighan. Then it was on to Breakfast.
In terms of Sophie Raworth, she didn't start out on the BBC News Channel. After presenting regional news (in the Yorkshire region, I think) she graduated to Breakfast News in the late 1990s, before moving to the Six in 2003 and she's stayed on BBC One bulletins ever since. She may have presented on the News Channel in more recent times, but I'm not sure when. She didn't start out as a rolling news presenter, anyway.