Would have to be balanced veeery carefully to prevent dual SN Bombers. The Barghest, Waran and Fafnir in particular.
The Fafnir has the highest power core of any bomber at 50880, the power required to fire two SNACs is 59480. This means even a 1.2x power upgrade will allow the Fafnir to fire dual SNACs. This means the highest possible upgrade is 1.17x.