It sounds like his employees just need a raise. If I was making $500k a year cleaning toilets, I wouldn't care about a career path. Obviously this example is extreme, but if losing people is a disaster, you should be paying them enough that it would be insane for them to leave unless they were planning a complete career change.
As for more responsibility, just give people more say in how the company is run. If your employers are better at something than you ever see yourself being, they probably have insights that you would never have. Ask them. Implement their ideas.
I don't think people really want to feel overpaid or overextended any more than they want to feel underpaid or underutilized. If employees are asking for more money or more responsibility, it's probably because they feel underpaid or underutilized, not because they want excess.
As for more responsibility, just give people more say in how the company is run. If your employers are better at something than you ever see yourself being, they probably have insights that you would never have. Ask them. Implement their ideas.
I don't think people really want to feel overpaid or overextended any more than they want to feel underpaid or underutilized. If employees are asking for more money or more responsibility, it's probably because they feel underpaid or underutilized, not because they want excess.