I had also considered laser cutting, but steered towards water cut due to the temperatures involved and the fact my case side is powder coated already.
Also wasn't sure about the cost differential between to two. I did speak to a engineering firm in leicester who does some laser cutting of ATR boxes for my company, and one of the cheif engineers said that it's fine on bare metal as it wouldn't create enough residual heat to tarnish surrounding material, but there was a risk with a powder coated/painted piece that it may ignite/discolour so they couldn't assure me that some rework of the coating wouldn't be required.