Excellent idea and one that I've pondered as to why they don't use more. Personally my recommendation is to use IR (Infra Red) light and a suitable sensor in the camera to read it. I have experience with IR flood lights with military night vision goggles (NVG's). Each one is equipped with a "flash light" (more used for covert signaling, but does work to brighten things up), but it can only be scene when looking through the NVG's. I can't help but feel this would help because they can make it as bright as they want, and it won't affect the subject by blinding them because they won't be able to see it. Just another visit I had from the Good Idea Fairy
Regarding your implementation, I would recommend against using multiple lasers. One is for accuracy (they have to be aligned perfectly of their lasers might not meet because of angle variations, and the further the focus point/subject, the greater this is exagerated, to the point where the lasers may not land on the subject together). Also, it creates multiple lasers to increase the risk of damage to the subject, assuming you are focusing on a person (I hope not, and if you are, please read into the damage lasers can do to human eyes, but I am confident this is not news to you).
To mitigate the need for multiple lasers, and to make the laser a bit less dangerous to your subjects, I recommend fashioning a "gobo." Short for "Goes Between," it is a common application to advanced strobism lighting. Basically you put something between your light source and the subject being lit. You may not be aware of them, but I guarantee you've come across them. Here's an example:
Using the same idea, just on a much smaller scale, fashion a grid of sorts using your finest (in terms of smallest, not nicest lol) sewing needles and place it directly in front of the laser. Use something that is not permeable to the laser light (thick and black paper should do the trick) so there are clearly defined dots leaving the laser as opposed to just the entire laser strength but diffused. Experiment with different size dots, number of dots, distance between the dots, etc.
This should also make it a lot simpler in terms of sychronizing all the laser dots to be triggered at the same time
Hope this helps, and I commend your desire to hack.
-Heie