Pat Kirwan has said in the past the ideal org structure is the one where the HC has authority over all football decisions, and that can only be the case if the GM is in a support role instead of a managerial one.
This is what Mike Lombardi (Now GM of UNC w/ Belichick) says as well. The best organizations are aligned under one single vision/program, and the HC is the ideal person to run it.
Now, all of that hinges upon having a CEO-minded HC, and those guys are becoming few & far between. Lots of these young HCs are really glorified coordinators who contract out the other side of the ball and don’t really know how to run a team and lead every part of the organization.