Remove the knob for the start switch. Design a replacement that requires the chuck key to function. After all, you don't need the chuck wrench when the chuck is turning. There are many different types of lathe switches, so you will have to come up with your own design. A small scrap of steel, aluminum or plastic and a few set screws is probably all that is needed.
I have used lathes for 45 years and I wonder why I didn't think of this sooner. Its a satisfying addition to your lathe.
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