I think the best model i have seen for a lean stdlib has been that of Golang. You have the standard lib and then you have the packages under Golang.org/x/ which

I think the best model i have seen for a lean stdlib has been that of Golang. You have the standard lib and then you have the packages under Golang.org/x/ which are experimental packages that sometimes end up being merged into the core language. The stuff which is not in the stdlib (TOML, yaml etc.) have been supported very well by community packages.