Making a high quality campaign is quite some effort and the engine still lacks some features, which would be helpful for this. A dialogue system is one of them, which already has a PR available: https://gitea.wildfiregames.com/0ad/0ad/pulls/8614

There is also a thread in the forum, where people are brainstorming about an official campaign: https://wildfiregames.com/forum/topic/123956-narrative-campa...