Just discovered this wonderful game, love the style and the units can't wait to see how it develops. The only part is that I wish the battles where bigger and longer. you could use move more, which could be improved by introducing into the skill tree and the same with the variations of units and that the world was bigger and had a lot more in it.
If you could also introduce more for each unit, like you could select the spear unit and specifically upgrade certain traits and elements. Such as defence or equipment and more variations as independent units for range, attack and strategy such as the trenches. Additionally if each unit had the same option as trenches where you could spend extra gold on growing a units numbers so that if you play on a huge map where you can take advantage of the size of your units.
Also if you offered more options for generating gold besides the tech tree that would be great as the gold is somewhat limiting you could do this by making each location captured be it a fort or a town. Depending on the size and difficulty to take to be be generate gold and also units, this might only be peasants but you can create specific groups such as ranged and as you upgrade the town not only thus the gold increase but defences and units. Additionally the map was a bit more fluid you would have enemy strongholds that don't change but you could have enemy units that move per turn.
Again love the game and am really interested to see how it goes if this was the plan all along then it's going to be amazing.