Currently the only way to modify a command block is to be an opped player that is in gamemode 1. I propose that we add a permission node that, when granted, allows a player to modify a command block. In order to do this, the method net.minecraft.server.CommandBlockListenerAbstract.a(EntityHuman) must return true assuming that the specified player has the permission node (as far as I know). I could probably add this into an nms patch, but my dev environment is a mess. If nobody wants to do this I could make a PR for it, but do you people think that this would actually be a useful addition?