I think we need someone who cares enough to make 1 like one of the few who made a mod!
I'm actually in the very beginning stages of my campaign for Sun and Moon, but I need to work out the storyline, settings, and characters before I start making the scenarios.
An important part of the storyline for the Moon faction is that there's an internal struggle between the path of wisdom and the path of savagery. It's something akin to any Star Wars game where you can choose to follow the Light Side or the Dark Side. This will effect not only how the story unfolds, but also what units become available later on. Following savagery will unlock units like werewolves and giants, whereas the path of wisdom will unlock units like the Moon Lord (a powerful magical unit). Also, I'd like for certain achievements to be able to provide benefits or penalties for the rest of the campaign. For example, finding a certain object might grant every unit on your side a +1 to sight range or pissing off that old witch might result in some kind of curse. I believe the ability to store data from one scenario to the next is essential to this! I also want a way to store hero data, but if it's just not possible, I think I can find a way around it. There should also be the ability to progress from one campaign to another, similar to how WC3 did it. In the beginning, two campaigns (Sun and Moon) would be available, and upon the completion of both, another would become available.
So, to sum all of that up, some of the things it will likely require are the ability to restrict the tech tree (i.e. you can only build a couple different units at the beginning), the ability to store data from one scenario to the next, branching scenarios (as I previously covered), and the ability to unlock new campaigns upon the completion of a previous one.