Aircraft substitutions - impact on flight/cabin crew

[Jack B]

For example, if a SYD-CGK flight has a 763 sub for an A330 for operational reasons, how does this affect the cabin and flight crew who are meant to operate the return flight? With the Cabin crew, since the 767 only uses 7 crew while the A333 uses 9, will 2 crew be nominated to pax on the return flight? And would the Airbus pilots also pax? Or would they have their slip extended?

The reason I ask it seems some CGK and MNL flights have been operated by 767s lately, however these may not have been "last minute" substitutions