This is all speculation on my part since I'm being lazy and not looking at the Score code, but it seems that influence started life as a signed 32 bit integer and limited to 2b. If it's now signed, that would allow a possibly easy way to make it 4b. Since HC did make a lot of the code 64-bit, that number could be increased quite a lot. However, I'm sure there would be a lot of code to screw with and it is a problem only for a smaller percentage and the ability to suddenly drop a lot more influence would give those with larger pockets and easier time to destabilize the market.
And as Poptart mentions, increasing capacity would just make it more likely we'd hit the bigger cap.