The amount of computing power required would be minimal. There's not that many carriers, lots of them have no meaningful market, or are in uninhabited systems, or are selling at well above the normal market prices (e.g. Tritium) specifically to players, or have restricted docking, or some other reason that this trade wouldn't take place. They could quite easily implement it so that if you're in a condition where your goods could be profitably transferred to a local market, the NPCs did do that without any need for actual player intervention - I can't imagine given some of the things they have implemented in the BGS that it'd be much effort.
However, I very much doubt that they will - it'd let you get a substantial amount of passive income from a fleet carrier with the only activity needed be to jump it occasionally between a couple of systems and reset the market. The principle of the game and especially of the BGS is that if you want something to happen, you either have to do it yourself or convince another player to do it for you. NPCs making your bank balance tick up just for owning a carrier - or making trade CGs considerably easier by letting NPCs load the carrier while you sleep, even if you did still need to unload it yourself - really doesn't fit with that.