An Elite Manei Domini (Gunnery 2/Piloting 3) has the following Implants.
VDNI (-1 GS, -1 PS)
Cybernetic MultiModal Senses (-1 GS)
Tripple Core Processor (Effective -1 GS modifier when determining the unit’s BV Skill Multiplier)
Artificial Pain Shunt (Effective -1 PS modifier when determining the unit’s BV Skill Multiplier)
To work out the new BV cost you modify the Effective Gunnery Skill by -3 and the Effective Piloting Skill by -2.
This takes the Effective Gunnery cost to minus 1 (below 0). How is this resolved in terms of the BV cost? The minimum the effective skill can be reduced to is 0, but then you effectively get the Tripple Core Processor for free.
P184
AUGMENTED WARRIORS (MULTIPLE ERAS)
The Battle Value for the various warrior augmentations discussed in this book are listed in the Additional Alternate Era Battle Values Table under Warrior Augmentations. Units using such augmented pilots, crews, and troops follow all other appropriate rules for Battle Value calculations.
In many cases, these augmentations may apply modifiers to the unit based on Skill modifiers, in which case the unit’s final BV is computed normally, and then multiplied as appropriate using the BV Skill Multiplier (see p. 314, TM). Through these modifiers, the minimum rating to which a Skill may be reduced is 0, while the highest rating to which any Skill may be raised is 8.
Note that the Clan Enhanced Imaging Interface is listed on the same table under Clan Invasion Equipment, as is the direct neural interface modification necessary to operate a unit via a prototype DNI, VDNI, or buffered VDNI implant.