Lots of my thoughts have been covered, but as a Metagame council member, I feel inclined to weigh in on this.
My short answer is basically, for what my opinion is worth, that a buffing process should be very similar to a nerfing process, with a specific focus on how we can thoroughly improve the mon as a whole, and not just for a specific metagame. I also think that if we have a metagame council, we may as well make use of it, right?
And now for a longer elaboration.
There are two parts of this to consider, in my opinion, and those are how the community plays a role and how the council plays a role. It's no secret that the previous buffing process, while interesting, yielded a process that was confusing and hard to follow. This ultimately was compounded over the course of the buffing process, and Voodoom's new state in the metagame is barely any different from before. Now this isn't to say that Voodoom wasn't buffed in a meaningful way, but I think it shows how tricky the buffing process can be to get right, and it certainly wasn't helped by a confusing process of having "Major" and "minor" buffs. Despite this though, those community members that WERE involved had very good ideas and were active and useful in progressing the discussion.
In contrast, the metagame council, as I recall, had minimal input on the buffing process which ultimately feels very backwards to me given that the council is supposed to oversee the metagame as a whole. Obviously the council isn't supposed to be the end-all-be-all authority on general processes, but in my opinion, for buffs and nerfs the council should have a far greater say in what ultimately happens.
Per precedent, we on the council do not ban caps in the current gen metagame, only doing so eventually for old gens, (see Aurumoth and Cawmodore in ORAS CAP). Therefore, if a CAP is either overcentralizing we don't have the means of actively banning it. This, raising awareness to an issue, is what more or less happened with the nerfs on Equilibra and early stages of Astrolotl, and the council ultimately decided the best course of action for how to "fix" these CAPs. While the effectiveness of these nerfs isn't the subject at hand, it does yield a glaring inconsistency between how CAP conducts buffs compared to how we conduct nerfs.
My take is basically this: We should have our buffs and nerfs follow a similar process, with the community discussing how a CAP should either be buffed or nerfed, with the council ultimately deciding what changes actually occur. This would include the community coming to a consensus somehow on picking a mon to be buffed or nerfed, though each respective voting process would have to be different somehow due to the nature of how different something overcentralizing is versus how thoroughly bad something is. I don't have a great idea or suggestion for this process at this time, though I think Rabia's suggestion is ultimately the simplest, and therefore, presently my favorite. It includes the community offering suggestions on how they would change the mon for the better, while still making use of the, otherwise underused, metagame council to make the final verdict.
To rebut those who are saying that the council shouldn't have the final say in the buffs and/or nerfs, I argue that the metagame council are the most thoroughly invested players of the metagame. That's isn't to say that there are very skilled players not on the council, but that the council is guaranteed to have players from the playerbase making up 100% of the votes. I do not mean to disparage the voterbase or the CAP community on the Voodoom process, but of the 71 votes in Major Change Poll 1, I am confident that at least a 1/3 (if not over half), of those voters have never played regular circuit tournament matches in the CAP circuit or are not well-informed of the CAP metagame. While this qualification ultimately does not matter for a regular process and SHOULD NOT matter for a regular process, buffing and nerfing are essentially and inherently strictly competitive changes. With the restriction on the final voting process to just the metagame council, there is a guarantee that every single person voting is well-informed. One could also perhaps argue that a "suspect testing-esque" requirement could work, but that's not something I would discuss now only because I haven't given it considerable thought.
To summarize again I think buffs and nerfs ultimately should have similar processes and I think the metagame council should ultimately have the final say in which buffs/nerfs are accepted. As for a slate of buffs/nerfs, I think it is extremely important that the community has a say in what is brought to the council overall as CAP is a community based project so I do think that having a period of thorough discussion to determine what COULD be done is essential.
EDIT: I'm also not opposed to adding more members to the metagame council too.