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Wow, not bad! As for ideas, I had a thought: it could be interesting to add some kind of heavy siege weapon as an upgrade. It would be really cool if the Cyclops' wall-breaking attack also worked on ranged attacks. According to the lore, the Ashan dwarves have something like that (although the design could be anything, even a ship cannon).
Design from Heroes 7: https://ubistatic-a.akamaihd.net/0004/prod/images/160708_Warfare/Fortress_Warfare_Siege_Full.jpg
Found it on Google (judging by the emblem, it was made by Nival):
Or, as another option, a dwarven weapon from the third Hobbit movie with a rotating axis around the shaft. It could be given magical attacks from the Academy mages and have a 2x2 area of effect, which would be very fun.
Another option is to create a launcher for horizontal rotating blades, similar to Warcraft 3. The principle is the same as in the previous point.
And finally (but not necessarily the coolest) - some kind of artillery weapon that fires at an area. The impact animation could be based on a scaled-down meteor shower.
But of course, it also needs to be considered whether this is feasible, given the game's limitations