In upcoming VRC Beta update, is adding native avatar size changing (yay!), however, it has some significant quality of life restrictions. It is limited to an opt-in world author setting (not instance creator) and a rather narrow range of sizes: 0.2m (0.5') to 5m (16').
Additionally, VRChat considers other ways to resize past the limits (e.g. goloco) to be a bug to be fixed, not a feature to keep.
While it is still in an upcoming beta, if folks could take a moment to vote and even comment their thoughts on these restrictions that would be lovely of you all.
Thread 2: https://feedback.vrchat.com/open-beta/p/1311-allow-scaling-beyond-the-02m5m-limit