Would more stable cordite leave time to stop a magazine fire?

Could more stable cordite have given crews more time to react between a turret hit and the resulting conflagration?

Very little, once fire had entered an open ammunition-handling route.

A short delay before the visible explosion does not necessarily give the crew usable time to intervene. Once fire has access through open ammunition-handling doors, a more stable propellant offers little practical recovery time. Keeping the protective barriers effective before a hit remains essential.