They’ve already done that.
It’s called “community college.”
You can’t offer a high-quality education with a turnstile, adjunct faculty. Your solution is wonderful from an economics standpoint, horrible from an academic standpoint.
Any business, even a pizza place, does better when they can attract and retain people long-term. People don’t stick around for adjunct faculty salaries with few benefits.
And who would write grants for research?
“Dear National Science Foundation: Hi, I’m Joe. I work 15 hours a week as adjunct faculty at State U. Please give me a million dollars to research blue crab larval drift in the North Atlantic. I’ve been here a year and a half. People say they really like me. I will use the money wisely. I’m pretty sure they’re going to rehire me next year. Feel free to call if you have any questions! Yours truly, Joe”