To use story points, you would have a linear model of some sort so that you could calculate how long, on average, a story point would take to complete.

If you know how to do that (the model), you could apply the exact same technique to the "estimated time" numbers to get a more realistic "expected time."

Changing from time to points won't improve the developer estimates at all; instead, it will further obfuscate them and reduce accountability, in my opinion.