War machines in Heroes V.

It's a pity that Necropolis cannot imbue ballistae with poison, or at least a poison cloud. After all, Inferno can launch such projectiles...
However, for the beginning of the game, the ballista is quite expensive (4500 gold), and by the end, other ranged units overshadow it... Of course, an additional attack would be good...
Maybe introduce a limit on the number of ballistae? At the beginning, 1 would be enough, and by the end, 40 would be operating. Then there wouldn't be such a power imbalance between units and the ballista. And make the increase, for example, every other week... It would be a dream come true!