I guess that with Meridian having "three" (well, two-and-a-bit!) sub-regions, it'd be a bit of a stretch. 40 minutes worth of pre-recording are required, regardless of which iteration of the programme will be 100% live at 6pm. To cram that all into the 5pm hour, with only 2 x 10-minute breaks between each edition, is perhaps a bit tight.
I do hope that the earliest pre-recorded edition doesn't start any earlier than 4:30pm though. Or, better still, 4:45pm. If we're gonna have pre-recorded news at all, then it should be recorded the least far in advance that is practically possible.