More variation in enemies, more variation overall e.g. storestuff, attacks (specials), storyline or at least a goal and seeing the enemies attributes would be great for a sequel. Btw ag upgrading all the time means not getting hit starting from lvl 20 or something.
Great potential for a sequel indeed. But the campaign is imo a bit too short and tanks came in too early. If the tanks came in later, there would be a bit more tactical play. In this game, I used the sniper hardly, built the officer twice and just went on spamming tanks and fire supports. It was easypeasy this way. Maybe some scenario's with longer reload times or something would be fun too.