Maybe this is just my perception but I've always regarded a World News shift as slightly more 'prestigeous' than a News Channel shift in a way as rather than just broadcasting to a few thousands in the UK you're instead broadcasting to many more around the world. So if World News presenters don't appear on the domestic News Channel not sure they're 'missing out' really.
I've been away the last few days in Asia and saw some of BBC World and liked most of what I saw - all seemed a bit more dynamic/lively than what we get on the domestic channel. Caught some of Global and Matthew Amroliwala was as good as I remember - he seems to handle everything with ease.
I think the world flagships (GMT, Impact, Global, B100D, WNA) are probably more prestigious than anything on the News Channel (possibly other than Afternoon Live and the Five) and The Briefing and Newsday and possibly the weekday overnights on PBS are probably in line with News at Nine and Newsroom Live but the generic weekend and morning world bulletins (and world news today) are probably less prestigious than anything on the News Channel. World has a number of presenters who seemingly have very little journalistic experience and little more in the way of ability who I'd imagine will never see airtime on a domestic channel shift.