If he can do it for fun...how long before someone else does it to burn and blind?
If he can do it for fun FRiend, then someone else already has a warehouse full ready to go.
In short, someone has to know a LOT about lasers and laser safety before he should even think about building that thing, imo, (and I'm not really sure this kid has all the knowledge he should have - he admits he's a little scared, which I doubt real physicists or engineers in a professional R&D environment worry about).
Make it 40kw and I’m in.