Basically I’m trying to use /sudo in a command block for the player that activates it.
Nucleus and EssentialCMDS doesn’t seem to have selectors for sudo in a command block.
Perhaps someone could make a Sudo plugin that uses selectors like @p in a command block?
Do you mean like the real linux sudo command?! Or could /execute command do the thing? http://minecraft.gamepedia.com/Commands#execute
Not the Linux command 
I’m pretty sure that /execute only works with minecraft commands.
Every attempt to use it with a plugin command ends with “Failed to Execute”
Well, akward, but didn’t know that.
That sounds like a bug. It should be reported to Sponge.
Crash logs or error messages in the console would be helpful too.
it might be that the commands you are using are somehow returning the wrong result, so the execute command thinks they failed.