In theory you're right but they couldn't fill the one they've got for the semi-final so not much chance of filling a bigger one. And like Liverpool's Main Stand extension, the loan would have to be repaid which means less for fees and wages.
Yeah like Arsenal paying back there stadium in about 10 years wasn't it, staying at Goodison Park though will stagnate them even more, better to bite the bullet build a 60k stadium and take their Medicine of Debt for 10+ years. Like most clubs though when they move to a new stadium they aka way get more fans.