Automation is the other solution. For example in Helsinki-Vantaa, there are far more automated passport check gates than there are traditional immigration desks: https://www.flickr.com/photos/bergie/3176184017

Even at SFO I've gotten to fill the immigration questionnaire a few times with a self-service machine, greatly reducing the time spent on the process.

They should definitely pressure the airport (to pressure the government) to create a few of those precious New Jobs and add some more people to immigration. It's just ridiculous in many airports, particularly in Europe. And it's been done, it's not like it's some pipe dream.

"Let's do the same amount of work with more people" opens the government up to a certain amount of criticism.

Do I really have to explain to them how to do their job?

You're the one suggesting New Jobs. By hypothesis, larger planes mean that arrivals are more concentrated, leading to longer lines, but not that there are more arrivals.