I would look at water jet cutting.
I have just had some Openbeam angle brackets cut in Rotorua out of 2mm aluminium. Designing and building an CoreXY Openbeam Reprap.
You don't get heat warping with water jet cutters.
Makes excellent cuts, only thing we found that cutting small 3mm holes that the aluminium is a bit soft and it blows the hole slightly bigger on one side, doesn't happen with harder steels.