I tried several times but failed miserably. Maybe someone else can get a functional PR?

I was thinking 2 events...

One to just ask if execution of the command is allowed through a command block. However this can be accomplished via the BlockRedstoneEvent somewhat. But I'd rather be safe and catch it at the execution level.

Okay now on to the real big and ultra-helpful one.

Looking at the source in net.minecraft.server.CommandBlockListenerAbstract, a method of customising buildCommands() would be amazing. I was thinking one of two things, events, or editing the SimpleCommandMap. However I can see editing the SimpleCommandMap leading to several large plugins breaking. (That's life but what's the point if there's a way to do it without it breaking anything).

So I was thinking have it call events. I tried and failed miserably, I also didn't know where to put and name the Event.