Hello. In addition to Starfy Wiki I'm an administrator over at Glitch City Labs.
We actually started affiliating with other websites not too long ago (including a French and a Japanese Pokémon glitch site) and we would happily support affiliation (if other wikis at NIWA are OK with this).
Regarding membership there was a discussion in the past in 2010 started by myself regarding whether Glitch City could become full NIWA members (I'm unsure if it is also on these forums, but on our side we had a discussion about it
here) and I was able to access the discussion because of being an admin of Starfy Wiki.
While I can't remember the exact details, if I remember correctly other members of NIWA weren't too sure about membership (Archaic noted for instance Bulbapedia already covers glitches, although admitted parts of the site about glitches were covered in more depth). One suggestion was to, rather than become members, for Glitch City to form a glitch alliance instead in which we would affiliate with Zelda Chaos (English Legend of Zelda glitch wiki) and potentially other websites.
Looking back, at that point the wiki had far less articles and the three main projects GlitchDex, AttackDex, ItemDex were still incomplete. I reflected on it and thought we should become bigger first. Have had similar thoughts about asking again recently, but been thinking of us becoming more exhaustive in our coverage (in particular in Generations IV+ and sub-glitches from all generations). On second thoughts however I feel we are at a better state than we were before (with 1390+ articles compared to about 300 in the past), so I have no objections, but I'll bump the older thread over on Glitch City to get some input.
Thanks for suggesting us and we would love to support further Bulbapedia too.

I'll attend the NIWA Discord chat to discuss if there is a discussion there already.