I would 100% would not book business class. Of course, it depends how important you value an empty middle seat and some food and your level of status but I personally struggle to see the additional value.

As for a cancelled flight or if the time was amended by 120mins or more, then you would be able to rebook onto any BA or IB operated service(s) providing there's revenue availability (i.e. if there's a seat on the plane vacant, as opposed to only award availability) very easily.