Customize permissions for commands executed by clicking a sign

[zml2008]

Minecraft has a feature that allows signs to be clickable, which in vanilla executes commands with the op level 2. Currently PEX represents this as having the console execute sign commands. We'd like to make that customizable.

What's the best way to represent signs?

• As separate subjects?
• As the player who clicked the sign?
• As the player who placed the sign?