[meta] Custom emoji: Will the current solution of custom emoji per group not get us in trouble in the future

(this is a meta discussion to make sure our plan of attack does not get us into trouble in the future)

Problem

At the moment we allow custom emoji at group level. And only at root group level (this might not be enforced yet, now I think of it)

But I have two questions:

Cross-group emoji

If group-a adds :tanuki:, will we in the future allow :group-a/tanuki: to be used outside the group? This is how I see it, but I'm not sure that's the best solution. It would be great to have custom emoji at user level as well, like :toon/doh: to show up as .

Instance-wide emoji

Say we want to build the feature where an Admin can add custom emoji at instance level, so :tanuki: will be usable in any group, what effect will this have on groups who have also set the :tanuki: at group level? I think instance level will have higher precedence, but I'm not sure.