How a carrier could change Force Z's options

If Force Z had a carrier, would Japan have to alter its advance?

Probably: a carrier would bring a fuller task force and better air coordination, complicating Japanese movement and potentially delaying operations.

The carrier belongs at the centre of a task force rather than serving as a lone aviation hull attached to Prince of Wales and Repulse. It would probably bring light cruisers, destroyers, aircraft, and staff accustomed to coordinating air and surface operations. Carrier fighters and reconnaissance could work with land-based aircraft in a way closer to British Mediterranean practice. The combined force might contest Japanese troop movement and seaborne resupply, forcing Japan to deploy heavier cover. That requirement could delay the advance and give ABDA more time to form and fight as a coherent force. The result remains conditional, but one carrier changes command, scouting, escort strength, and logistics simultaneously.