Well, the way I've seen it deployed is much more relaxed through Discord. Developers can be broken down into three categories; coders, mappers, and modelers. The way a lot of communities do it is have public channels for each of the three categories, where developers and contributors can come together and discuss things they're working on or things they need help with. Suggestions are also implemented in a much more relaxed way, where there is an additional channel where anybody can just brainstorm ideas and spitball with other community members. If a dev or contributor likes an idea, they make it and request it to be implemented.
Typically, these larger dev teams have a lot of internal structure beneath the owner to facilitate ease and effectiveness. The team I'm apart of has pushed out over 700+ updates since going open source four months ago because of how efficient the system is. People higher up the chain on the dev team who approve merge requests are more so responsible for quality control and direction of the server than the average dev, and so on and so forth. Lead modelers and mappers have the final say on art direction and aesthetics, etc etc.
In the context of GG, the dev team would autonomously generate content, and Garnet's role would simplify to merging content to the live branch of the server.