Hi there Blair,
It definitely isn’t advisable to change core plugin code unless absolutely unavoidable for this kind of reason 🙂
I’m not sure it’s necessary to tackle the problem that way, though:
We would like to display the timezone (EST) on any events that are slated for a specific start time (ie live webcasts). Can this be coded in and not affected by updating the plugin?
We add a ton of action and filter hooks on top of those provided by WordPress itself, in addition to a template system that makes it easy and safe to override specific templates.
I’m not completely clear on where you want this change to be implemented, but perhaps the tribe_events_event_schedule_details filter hook could be leveraged here? Could you pass that across to your dev and see if that helps?