Just a minor note, to those of you requesting icon and color formatting in the chat strings. I believe this already should be possible, using the same markup notation used elsewhere in the game, such as the rollover help.
I believe the format is (though I don't have the source handy to look it up right now):
<color="r g b">
<icon="(32)(iconname)">
(that 32 is actually an adjustable value for the width of the icon)
Similiarly, it is possible to implement "not" and "or" operations (albeit in an awkward fashion) by using multiple triggers. For instance, have trigger A be not active, but have your real effects on it. Then have trigger B and trigger C, each of which represents the conditions you want to logically OR together, and have their effects activate trigger A.
In regards to multiplayer behavior of triggers, unfortunately some triggers have to be limited in multiplayer for security reasons, but where possible, we try to make sure it works on both. In some cases (like the issue with GPs we fixed in the patch) it was merely an oversight, and not a "deep" issue causing the problem in MP.
Some great suggestions so far, thanks!