A better way to get a pool of talented young lawyers into public service would be to require them to serve three years of duty as public defenders and/or prosecutors. This would occur after passing the bar exam but prior to being admitted to the bar. It would be not unlike the internship and residency performed by physicians.
Every subsidy will just make college more expensive.
Why do we need lawyers? Why can't people mediated their own disputes? Why do we have to give criminals constant and continuous reviews of their convictions? Lawyers are a protected class of criminals; the good ones need the bad ones to stay in business.