Aren't APUs relatively small? I would suppose there is a tradeoff between a heavier, more costly, and more reliable APU with the increased fuel costs to cart it around and the current situation. Other systems have improved because they decrease fuel costs to do so.
I would expect a more even solution is to improve the operational monitoring of the APUs to detect when their performance is dropping off and make a schedule for replacement on that basis before it shows up as unacceptable operation in use. Clearly the decreased demand for cooling in the Winter could mask this decline and monitoring might catch it based on previous measurements through a year long cycle.
But abuse? Yup. Bane of my existence.
me: What does it say on the label? 400 pound limit. What's on the broken item now? 600 pounds. Why? Because it still worked OK at 550 and this is just a little more.