Regardless if job requirements change (they only will for a subset that no one cares about and no one is trying to get), you're going to screw people over. The lag time between no-loans and job-requirements dropping is going to be too long. There will be a lot of people who fall into the cracks and will be stuck with the lowest tier jobs because they couldn't afford a cash-only education until it was much less expensive.
Regardless of this - I feel like this is the wrong approach to debate lower costs vs no loans vs whatever-where-a-student-pays-in-the-end. I think 4 year college should be free (no tuition, books paid, stipend or special housing, etc.) given how the world works. I went to college for free due to CH 35 of the VA and it was really the only reason I was able to do it and fully commit to it. I have no problem with having a more educated populace - regardless of what they study. I did study something that came with very gainful employment but that wasn't obvious in the beginning of my studies. I think 4 year college would be less necessary if we had better education from the start - but we're never going to get there in this country.