OMG these MyGPTs are freaking awesome! I am so excited for the potential of these! I had a couple of thoughts that I am guessing you guys are probably way ahead of me on. 
But I wanted to get them in because I haven’t seen any conversation around this yet beyond the announcement.
It would be so empowering to have a way to maintain a user contexts for api calls. Some kind of persistency in MyGPTs. An anonymous context would do wonders. For someone to be able to come back and continue an app session would greatly increase the value of the app. And we don’t need any personal information. Just a way to to track a persons history anonymously would give us so much ability to tailor the user experience.
Second, the use of controls. A way for users to interact that doesn’t require them to type things out for follow up. Similar to the way we are asked about which of two follow up choices are better or if the response was better, worse, or same. Radio buttons, checkboxes, etc… A way for us too make follow-up and interactions more streamlines for the users.
Thirdly, images or styling that we can add to the app responses. I know we are trying to make these non-programmer friendly, and that is awesome. Buy if we could add html to our responses or “templates” to our responses that we could add styling to, we could greatly enhance the user experience.