Yes. Agreed. As far as a live GM mode goes, maximum freedom and power to the GMs -start there. A group of participants who fully trust each other should be the target audience for GM mode development. The bar set at the highest level so to speak.
IF, that is IF the developers wanted to appeal to varied styles of game play in live GM mode, the following approach could also be considered-
For the players and GMs who aren't familiar with each other's style of game play, have those folks be able to seek games or events with other GM permissions.
Don't want the GM to be able to flat out kill your character? Join a game where that is toggled off. Don't want the GM to be able to help you? Join a game where that is toggled off. Don't want the GM to be able to etc.? Join a game where that is toggled off.
This approach, default maximum GM power, will most fully utilize the scariest, most exciting and versatile tools of role playing -the brains of the participants.
Sword Coast Legends either missed or misjudged the default max GM power approach, and are now in the process of trying to add more DM/player freedom. It'll be interesting to see how the SCL and D:0S II GM modes shape up.
Nothing quite gets your attention like a human (GM) being able to call the shots in a live computer game. The ultimate "game mechanic" -a live GM. Start there and I believe, everything else naturally follows making this the best live GM mode it can possibly be.