This. My experience on Second Life and Koikatsu showed how hard it can be to get things to line up to look right.
To jump in and throw my own two cents into an argument that I don't think any cares
really strongly about, I have to disagree with both yall there.
This is made in Unity. So the hardest "part" about this would be reliant mostly on the dev's side. If they animate everything per character, rather than using presets that are tweaked, yes. You would be correct.
However, if they use presets they made themselves that are just applied per character, with tweaks for scale, size, etc. it wouldn't be hard at all.
What I mean is that it wouldn't be a hard idea to
implement. But the difficulty in doing it would then be passed off to the end-user in tweaking scale, motions, etc. But, we all know how dedicated perverts are. Just look at Skyrim and how blessed some of that stuff is there. BUT Unity eases so much of that it's almost a non-issue.
tl;dr: It wouldn't be hard. It's Unity, it is well built to end-user post-release application tweaking. There's a reason VRChat was as popular as it was. But I wouldn't hold my breath, because the devs would still have to release an SDK to allow that sort of thing. Which is a different development branch entirely.