Undergraduates with family income below $200k will be tuition-free at MIT

Or, crazy idea, have the government pay all tuition up front for everyone and then collect an extra .5% on your income tax for every semester you attend (or .33% for every quarter). Obviously you'd have to put some limits on what colleges can charge to get paid from that pool of money.

Then you can't go broke from debt because it's a percent of your income, but it's also not "free" to address those who have concerns with that.

You could apply it to all outstanding school loan balances too. Get your loans paid off in exchange for an extra 4% income tax.

I actually quite like the system we have in the UK.

Graduates pay roughly 9% of their income above £27k towards debt repayment, and the remaining balance is written off after 30 years. Typical tuition fees are just over £9k per year.

This strikes a nice balance between encouraging people to carefully consider alternative non-university careers whilst also not preventing too many people from not being able to afford it.

Note my numbers are approximate because they can vary depending on when & where a person went to university a couple of other factors. Also I do think the system could be slightly improved (especially around maintenance loans) but on the whole has a good structure.