I'm not so sure the positives outweigh the negatives with regards to ammo. Though really I need to see more of the game and how the mechanics play out at the moment I'd say leave it out.
If the game plays out in a realistic manner without the need to bring in ammo supply mechanic then as I said leave it out, however if it is obvious during play that units have unlimited ammo then there is a problem again it's tough to answer without seeing the game in action or playing it for awhile.
I think you need to base your thinking on whether the game needs the mechanic to stay within realistic boundaries or not.