The way to make it solvent is to convert it into a semi-defined benefit plan, that is - make the benefits flexible instead of fixed. You'd have your baseline of 100% of the theoretical benefit (say it's $5,000 per month for a given retiree). And if the plan is fully funded, everyone would get their theoretical benefit amount that year. But if the fund underperforms and becomes only 70% funded, then everyone gets a 30% benefit cut that year, so that the fund is always forced to be 100% funded. The person who'd get $5,000 then would only get $3,500 per month, and re-assess every year. Drive the benefits to the level of funding, not the other way around.