Hi Scott,
There is another way to enable the Enable extensibility features option by using the On-Demand Services API - Integrating third-party systems with AEM Mobile
In order to turn on the extensibility feature there, you would have to set ‘isTrustedContent’ to the true at the article metadata level -by default, it is set to false.
Please check out the Downloads section of the above article and consult the Entity Definition spreadsheet for more information
Thanks,
Andrei