I disagree. This will make killing light battleships using a heavy impossible. I do agree with introducing heavy anti-shield weapons for battleships, though. This would fix the balance between heavies and lights.
But there is still a problem, although not huge. It would make the Valor, already the best battleship in the game, even better in comparison with other battleships. It could be solved by turning the forward gun into an anti-shield weapon which drops a battleship shield in one hit. It could also fix the Valor balance, as the FG would be less of a critical weapon and thus the ship wouldn't be so unfairly better than all other battleships any more.