As a Roblox developer, it is currently impossible to do as the Roblox official wiki describes, and that is to give specific users permission to join TeamCreate for a game.
Your first thought is likely “just rank them up in your group.” But that would mean giving people access to work on all games in a group. Hiring developers, though, often means you want them accessing only one game. This has led a lot of teams to create one group per game, which is far from optimal.
The Roblox wiki already says that anyone with the permissions in the group rank to “create and edit games” has the ability to add individual users to the TeamCreate, but that’s not true. However, it should be.
This very system is already in place for user-owned games and already works. Adding it to group games would be tremendously helpful to organization for game development teams. And, given that it is already functional for user-owned games, I hope it is also a simple tweaking of permissions systems and UI, so that this isn’t something that has to consume many hours of engineering work.