I'm sure there has been someone that has used a different type of clear coat on a machine. I am not fond of those that paint machines simply for the reason of changing it. I think that even pretty bad looking machines should be preserved as much as possible. Have you looked at
Cleaning and repairing the Shellac clear coat on Vintage sewing machine heads I know it is a long thread, but that would be the best way to maintain the machine.
Janey - Neat people never make the exciting discoveries I do.