There should be more to the game than just levels e.g. unlockables like new maps, new weapons etc. You should also be able to freely change your team and character, its not so fun to be stuck with the same character throughout the whole game.
It would be badass if we could find weapons and equip them to soldiers, and them being able to gain experience, as I really don't think they all have the same weapons and have equal combat experience making them all them do the same damage, also leaders should be more versatile in fighting, as the only thing they are useful for is recruiting, other than that being identical to an ordinary survivor. which doesn't seem to be a problem as survivors show up almost every 3rd day. Hoping for a sequel, this game is awesome and deserves 10/5 stars.
By the way, "mercenaries" actually should be "merchants", as when you approach them it says something about "peaceful mercenaries", because mercenaries are actually hired soldiers in real life, you can see that they actually should be merchants. Other than that, the game was great except for the occasional glitches: 4/5.