Hi Sam,
I know this is a dated request, but I have a use case that would benefit from this feature of “pinning a topic within the tag archive UI”.
In my case, the option you laid out above that makes the most sense is (also) “2”:
Admin chooses which of the 3 tags it is pinned to? (maximum 3)
In my current case, I only need to pin it to one (of many) related tags.
But in the interest of flexibility, having the option to choose which tags to pin the topic to would offer further advantage.
Just thinking - are you still liking the idea?
Thanks