Except it cant? It can't mess with the Akashic Record itself, its not on the level of the Akashic Record, it's not any of the things you stated. It's a wish granting machine that returns a result depending on the amount of power it has at its disposal (except it was corrupted so it basically just wrecks shit and births Angra Mainyu). At the height of it's power with seven Heroic Spirits it can theoretically allow someone to gain access to Akasha once (or it'd just wreck shit instead probably). Gil used that power to cull humanity. That was his wish.