I'm not sure, but I think if a carrier was full of T9s filled with cargo, they would all have to belong to different players. (In a normal Shipyard you can only get one shipload of cargo in, no matter how many ships you have there). Will it be much quicker for the carrier to jump to a system and all those T9s to unload, than it would have been for all the T9s to fly there straight?
Alternatively, if the carrier is full of cargo itself, will loading it, jumping it and unloading it be much quicker than the same number of T9s just trucking?
I think the carrier ways might actually take just as long, in which case there's no net effect on the BGS.
The problem is you can set your own price on the carrier. So you could sell something to yourself for an inflated price and then sell it to a station at a loss, resulting in neg inf for the controlling faction. If you do it right you yourself only have a small loss or even a profit if you get cargo from out of system.
Same for pos trade inf. Buy stuff, sell it to your carrier, set buy price low, buy it again from your carrier, and then sell it to the station at a big profit.
Instead of 10 trade runs you just need 2 from your carrier and as you filled it up with cargo you just need to run between your carrier and the station the following days until it's time to fill up again. It's even more viable now with the shorter jump times.
The station only uses the buy from carrier/sell to station difference to calculate the inf gains/loss for the bgs.
The hydrogen bomb: jump your carrier close to station, buy hydrogen or any other commodity from station, sell it to carrier, buy it from carrier at max price, sell it back to station for "big loss" = tank inf for controlling faction.