How does confirming the right of the people to keep and bear arms, to be free from infringement by both federal and state laws “centralize power”? It seems to me it disperses some very real power.
Look at the history of the incorporation of the 1st Amendment. Local libraries forced to allow perverts to view pornography on their internet terminals by federal order, townships forced to remove crucifixes from public lands and nativity scenes from their town squares, prayers in the local public schools silenced, the Ten Commandments ripped out of local courthouses by order of federal district court judges, etc.
Let's assume that the newly reinterpreted 2nd Amendment gets treated as it was by the Nunn decision you posted. The federal courts decide that concealed carry isn't covered by the 2nd Amendment and that it is somehow antithetical to whatever they decide is valid gun ownership as they create new law from the bench. All of the state "no carry" and "concealed carry" state laws could be voided in favor of the one size fits all 2nd Amendment jurisprudence evolves into, consistent with the ban speech in order to protect it precedents of 1st Amendment incorporation.