Hire more people to do what? Be on-call?

Hiring more people is a great idea for making on-call less stressful, because it allows for much sparser on-call shifts (e.g., one week every 8 months vs. one week every 2 months). But I don't see how hiring more people gets rid of on-call completely. Someone will always have to be on-call.

You cannot just hire people who do on-call-only duties and nothing else, you have to be very closely familiar with the code and features being written in order to resolve issues effectively. Which usually means that you need to be someone who actually worked on those things, not just some glorified extra-fancy customer-support worker.