For 1/4" max thickness, you might consider a manual punch like a roper whitney number 20. This is a 20 ton, manually operated punch- you bolt it to a workbench or hold it in a vise, and turn the handle, and it punches a hole. They use standard ironworker punches, availabler from Cleveland punch.
They are often available used or on ebay for a couple of hundred dollars.
Yes, they require muscle to use, but thats supposed to be good for you, and its cheaper than paying for a gym membership.
But they work, right out of the box, so to speak, without engineering, rebuilding, testing, and so on.
For smaller quantities of holes- 20 to 50 at a time, they are surprisingly quick, and easy to cobble up stops and tables with a little scrap metal, a few visegrips, and maybe a stick welder.