I love the idea of adding UU 1v1, but I think it's way too soon. As someone who actually
played UU 1v1 when it was in PL (albeit I was 11 years old at the time), I don't have any good memories of my time in that slot, nor do I have any of watching other people. The problem, which occurred then, and I 100% predict will occur in WC if it is added, is that UU is just not played enough outside of teamtours in order for
useful resources to be made. People didn't have any sort of VR, sets comp, or sample team dump to understand how the meta functioned, so they ended up just going down the list on the SM VR until they got to the best mon that wasn't banned, and built around that. I predict the problem will be much the same given the fact that we have less than a month until WC starts.
I italicized the word
useful in "useful resources" in the last paragraph because any council can come together and make ""resources"" for an Other Tier and tell you that it's developed. You can play all the friendlies you want and speculate about what's good in the builder, but the truth is, metagame development can only truly happen from consistent tournaments (and ladder), and UU just does not have that. Not even to mention the fact that UU changes every three months, so a lot of real metagame development goes go down the drain every time tiering shifts happen. It would be pretty much impossible to maintain a consistently updated sets comp and VR if there's not a UU tour pretty much every month in between teamtours, which I don't expect to happen, especially not one right now.
I don't support DPP either. The simple fact is that we have an entire teamtour dedicated to oldgens now, so we really shouldn't go back further than BW. NatDex is also a meme (ban Tapu Koko wtf!).
That leaves us with three real options: a fourth SV slot, SS Bo7, and Multigen. I'll throw my support behind
SS Bo7 because I don't think anyone wants to watch another SV slot or go through the torture of building Multigen again.
FTR I also support having a flex slot (like the two in OGPL); not sure how that would work in a pools setting though.