I think if you can only attend a small amount of meaningful tournaments and place well, you should be placed high(Like Gungnir and Verm). However, rather than move players down due to inacitivity, I'd keep players where they are and move players above if/when necessary. Scenarios where this may happen involve players that get consistently good results, so they are rewarded for attending many tourneys and placing well, but those with less opportunities aren't penalized.
So if we have say Gungnir in S for great but few results, we keep him in S and move players above him. Technically they're moving down, but I think it's important to keep them within their respective tier until they give us a reason not to. I think inactivity can be a reason to drop, but only if it's complete inactivity for a lengthy amount if time. If a bunch of people passed Gungnir on the list, but he stayed S I don't think there'd be any issues. But if he totally stops activity with the community for like a year maybe, we either put them down a tier or put them in a MIA tier so we don't necessarily discredit their previous accomplishments.
Also, I think S tier should be reserved for players who do get results, because I agree with Kalm that a lot of factors come in to play and to fight against them and still play well is a test of their ability. I think those of us that have been in a tourney setting can attest to the amount of pressure, among other things, that can drastically affect our performance.
Last thing I wanna touch on, I think community input is important across the whole list. I think a2 has done a pretty good job, but I think having the community freely voice their opinions could benefit the list. Like if the vast majority of us disagree on something we should speak up, we all have different and valued opinions.
Despite disagreeing with some things I do want it to be known that I appreciate what you've done a2. I know not everyone is too big a fan of this list but I like that we can have a layer of competitiveness despite playing a terrible character lol. Plus it gives aspiring playersan idea of who to study, which is key to a lot of players improving(LoveExpert for example).