[bbctvtechop]

I think you're a bit confused about what's happening tomorrow. 
All that's happening is the joint daytime output is from E (apart from the 1pm hour when World moves to C), evenings (7 - 10pm), overnights (2 - 5am) & World early mornings (5 - 9am) from C.
World & the NC have been joint all weekend, there's nothing to "change over" and no "new system" is starting tomorrow.

Other than there'll be no way the BBC can provide UK specific Breaking News for the month. Technically impossible by all accounts .

Not sure anyine has said its technically impossible. Just that (presumably) there is no shift dedicated to it in either the editorial or technical side until the launch in April. 

I assume this is because all resources are being put into piloting the new channel and making physical changes to studios.

However I'm 100% confident that should a situation warrant it, some way will be found to opt the UK feed out of the World feed.