I am not sure on the thickness you are working on, but I have worked on a some thick aluminium frame years ago and I hired a nibbler that suited up to 2.5mm thick, which when was clamped up inverted, gave very good control after some practice. This could be too slow if you are making production runs, but collection control of the chips would be able to be recycled or sold to scrap metal guys, otherwise looking at the idea of stamp cutting with a strong press could be another option, especially from soft copper sheet material.