I feel as though there's no bonus to hitting zombies going super fast or just tapping into them. Maybe factoring that in would make running zombies over more useful?
Needs some way to control your troops during the battle - they do the stupidest things sometimes ex clear out all the other buildings before attacking the tower...
Pretty much every customer offers you a price below the market value. It costs you more to keep these people hired and for them to make you the product.