I just discovered after some testing a potentially useful function for /click

/stopmacro

Here's what I just tried:

/click MacaroonButton96
/click MacaroonButton97

On MacaroonButton96:
/stopmacro [harm]
/cast Spell1

On MacaroonButton97:
/cast Spell2

If I don't have something hostile targeted, Spell1 will cast and Spell2 will fail because of GCD. If I do have something hostile targeted the "sub-macro" will fail at /stopmacro and then the "master-macro" will cast spell2.

This has potential because it means you can almost form a logic branch with a macro. Not exactly ... but it is better than just having a single hardstop.

Thoughts? Impressions?