Balance in HotA.

Perhaps what I'm about to say will seem like heresy, cause rejection and confusion in immature minds, but why does every hero have a catapult from the start by default? In the good old King's Bounty, as far as I remember, to kill a villain in a castle, you first had to buy a catapult in some town. What if we brought back the old traditions, removed it from heroes by default, and made it an object that can be purchased? This would strengthen the weak ballistics skill (if you can only have a catapult if you have the skill), and at the same time, it would add some balance, as castle walls would give the defending player a greater advantage. To further enhance ballistics, you could add some banks to the map with a good reward, where you have to fight a garrison and preferably an archer army - this would make ballistics a very useful skill at the start, when there are many such objects around, and the reward in them would give a good advantage in development during the first week.