The biggest problem is how to get the people doing the hiring to care about your new magic metric. You could devise some amazing algorithm to calculate a researcher's impact, but if nobody on a tenure committee thinks it's a valid way to rank researchers then it's not going to go anywhere. This is where you hit the most inertia in the industry. The people making hiring decisions look at which journals you publish in and they care about the journal's impact factor and historical prestige. It's the fast/lazy way to judge a candidate. It's going to be hard for a technical solution to the problem to address that sociological problem.