I doubt this will help most folks here but here's how I've been cutting leather lacing for ten lustrums . My needs are perhaps less exacting than are yours. I make very thin spiral cutting dies the length I need. I can make a die in about 30 minutes using automotive hose clamps, steel rule cutting blades (either 0.014" one point, or 0.028" two point, both 15/16" tall and center bevel.) See pictures. There is some material waste but I consider it acceptable due to the massive reduction in my labor. I don't need to edge the grain side because die cutting rolls the cut edge over by it's very nature enough to suit my needs. It's a great way for me to still utilize my scrap leather. In my youth I'd spend a lot of time in libraries and read that this is how the American Indians made their lacing. It ain't my idea, but I modernized it. You'd need a small but powerful press. Small hydraulic ones would be just fine. I stretch the lace to make it straight.
The cutting die:
The cutting press
lace:
I have made dies to make lacing that is much longer.