@Amosfriend Wrong on a few accounts. The ammo glitch has been fixed for many users. You can exchange whatever weaponry ANY character has by dragging the weapons from below and letting them take any of the six spots above. You can reset a round back to level 1 by losing and pressing "Restart." (Not "Continue at last checkpoint.")
@231ving Hover over the green Army storage box on the bottom-right and click on the spiked grenade icon. At the Item Screen, click on any of the five items below to remove that item from your roster. Finally, click on the Small Medkit to add it to your roster. You can now use that item in battle.
@jay234 You can kill air units. You just have to click on them. Unfortunately, your melee units still charge forward to take on other units alone. This makes it more of a pain than it should be. Sigh.
@dvz458 For the sake of informing everyone else, I'll post the answer here. I don't think that's possible. However, you can reset your Soldiers' skill points if you think you placed them in bad spots. Just go to the very right on the Skills Screen of your Soldier. (No idea if it costs money though.)
@xlxs You obviously have not played the game since the update times are updated to be a lot shorter. Of course, that requires not jumping on bandwagons.