Delinquency is also mostly just about being a leading predictor of foreclosure or some sort of renegotiated payment structure. The same stat suggests that foreclosures overall peaked at just over 2% (but up to 15% subprime) [1 again, but also 2 which is more clear on 2.23%].
So I’d assume something closer to 2-5% foreclosure, depending on your estimates of benefits policy. Even in foreclosure, there’s still recovery (financially).
In fact, Goldman Sachs might even make a profit re-selling the mortgages it bought off of Fannie / Freddie as part of its $1.8B court-mandated “consumer relief” program [3]. It’s unlikely the Fed would be as “good” at this as Goldman, but a likely unwinding strategy would be to sell them to similar investor groups. Either way, not going to $0 :).
[1] https://www.statista.com/statistics/205959/us-mortage-delinq...
[2] https://www.google.com/amp/s/www.statista.com/chart/amp/1546...
[3] https://www.google.com/amp/s/www.bloomberg.com/amp/opinion/a...