This stuff already exists, for Warcraft 2. But it gets little to no visibility at all.
The mods. Take a look on youtube about Warcraft II mods by 2 guys who have been into it since like 2018 or 19.
Over 20 tilesets across different from these mods.
New campaigns, completely new plot
New units and abilities
For now, no new siege unit
Footmen have e.g: Footman shield ability now for late game.
Quality of life features ? This is where it turns interesting.
stuff like rally points, flags for such, shift command, training queue, animated buildings, smarter AI to attack, base game AI fixes like multiple island to attack, training goblin sappers/demos, unused abilities are now used like invis, raise of the dead, runes, many more stuff
A new campaign tied loosely to WoW lore could work as a crossover event. A fresh tileset would refresh the visual feel. Adding new ground, naval, and air units would expand strategy depth. New defensive towers and a siege unit would also shake up multiplayer balance.