Hypothetically speaking of making such a mod,
Kingdoms: Impulse, GamersGate,...
Empires: Steam,...
The Sovereigns would be the CEOs or whoever has the power there. Lord Froboy for the Impulse Kingdom.
There wouldn't be Elemental Shards. They should be something like Publisher Shard, Support Shard, Infraestructure Shard... So the most powerful tactics would require a certain number of them. You could cast Ads for extra Prestige for your Kingdom/Platform, release new games ("I cast 'Elemental: War of Magic'") for extra revenue,...
Cities wouldn't exist. We would get Sites. In those Sites forums could be built, as well as extra infraestructures for digital disitribution, training camps for adamant and militant fanboys,...
Most "important" users (Karma coud be used for Stardock forums) would be featured as Heroes that could be recruited. There would be different power levels (and maintenance costs). For those worried about Karma: 20+ Minor Hero; 70+ Hero; 120+ Great Hero; 200+ Epic Hero. Users like Annatar would be given automatically a rank and role in the mod similar to those of Dragons in Elemental. So if you were hoping to recruit Annatar easily, forget about it.
Tech trees would reflect the nature of the mod, with techs like "Improved fanboyism", "Advanced Flaming", "Shady EULAs",...
Hypothetically speaking.