Well i got the Germans as my protectorate in my gaul game this time... this time it seemed a bit more realistic as they accepted right after i smashed their full stack of spear warband + several women and axeman that was hanging around my capital... (huge victory with the X mark too.. i had less men but killed them all losing less than 100 attackign up hill too rofl)

But again the Romans never gave in dispite being pounded to dust with at least half a dozen X over the italian with all 4 Roman factions suffering catastrophec defeat in my hand... i think their are probably some particular match ups that will never give in (Romans giving in to Gaul for example)