Based on what happened, it looks like some simple strategies will help to mitigate any further incidents, among them might be ...
Getting numbers onto the bottom of the cars is job one. Simple job, too. All they need is weatherproof reflective stickers. I'm betting they are probably being printed in a factory somewhere right now, and will be on trucks headed for WDW by tomorrow.
Almost all guests will have phones. Disney should create an emergency automated text info line. Post the number in the gondolas, so that in the event of a widespread outage, you can dial the number to sign up for the texts. Above all, do NOT attempt to obfuscate what is happening and what the plan is. Guests WILL get info off Twitter, and it may be nonsense or not, so stay ahead of that. It's not that hard. The regular audio should switch to soft music during any extended stoppage.
A manually-operated pallet jack type device should be stored in every station, that can be used to quickly move a disabled car off the line. If you have to tumble the thing into the grass temporarily, then do that -- one damaged car is better than the PR value of a major stoppage. Maintenance should not have to bring this in when needed, so that traffic issues don't impede access. (Doesn't matter if it will never be used; having belt AND suspenders clearly in place will help guest confidence.. Put it all in a shed prominantly marked "Safety equipment".) Personnel can walk in cross-country if need be, but equipment is slower to move, so just store it on site to save time.
Also, for a while at least, parties should be given their own cabin and not have to share. A big part of what upset people in this situation was being "trapped with strangers", so eliminating that as a factor should also help restore guest confidence. (I know it would lower the load factor, but right now that is a minor issue.)