I'm only in my 9th day of developing this game, so I'm only covering the basics. I plan to add about 5-6 more different units + 1-2 neutral NPCs per location. I plan to diversify the gameplay with waves of enemy units (between waves, you'll be able to upgrade units or buy new ones) and more UI. I also want to create a global map where we can travel and get into various troubles along the way.
I also want to give the player the ability to upgrade various abilities and use them in battle. I want to add enemy archers, cliffs in locations, and much more.