What about and older machine with a knee control for speed? The older knee control machine were mounted in a cabinet. I have a vintage singer with a knee control that is an absolute workhorse. It was my Mom's old machine and she sewed pinch pleat curtains, thick wool coats ... you name it that machine handled it.... and still does. I have a few decorative stitiches but really use it for straight sewing and zig zag.
Industrial machines have a foot petal that is often mistaken for speed control, its actually a brake. If you do lots of really heavy stuff maybe an industrial machine is your best option , but even used they can be a bit pricey. I have friends that have them and I am so envious... the sew faster and are just really tough machines, but typically only perform one stitch.