12 gauge = 0.109"? Water jets do have a bit of taper to the kerf but that probably varies by machine & fluid & program. Laser might be another option. Both might suffer a bit by the piercing hole & how they close the path without a burr or overcut. And then there is a tolerance as to how close they follow the path. That's a pretty high density of pretty small shapes. Some shops have both laser & water so would probably tell you more about pros & cons just looking at the CAD file. Is there a specific design reason why they have to be hex vs round holes?