Sure it is. You move from the person moving the hay to the person designing the hay moving systems. This would be a perfectly cogent career story for any engine

Sure it is. You move from the person moving the hay to the person designing the hay moving systems. This would be a perfectly cogent career story for any engineer working in agriculture, and I know plenty of people who have worked in higher-margin areas of agriculture who have made the jump. (Beekeepers learning biochemistry and getting jobs working as Honey Q/A scientists, chefs jumping into food research and development positions, farm owners pivoting to seed banking/specific organism sales, etc.) The fact that you can't generate enough economic surplus to fund studies to acquire the additional mechanical engineering study in a manner competitive with other mechanical engineering students is why you view the path as untenable. Hence why these positions are desperation tier end-of-the-line jobs and why the CoL/Wage arbitrage is required to keep them staffed. Similarly, people engaged in agricultural studies generally don't come out of the 'harvest labour' workforce. Working on a farm is a transaction with a specific expected ROI. If the ROI sucks in comparison to other mutually exclusive exchanges, why would you do it?