You could do a lot of things. Rust had a gc and it was removed so they have already explored this area and are very unlikely to do so again unless there is a big need for it that libraries cannot solve. Which I have not seen anyone that actually uses the language a lot see the need for.

Not like how async was talked about - that required a lot if discussion and tests in libraries before it was added to the language. GC does not have anywhere near as many people pushing for it, the only noise I see is people on the outside thinking it would be nice with no details on how it might work in the language.