The point is there are countless ways to view activity. For example in PSL you can see countless players with low ladder ranks still doing well in their battles. It would be naïve to assume that their knowledge about the tier is insufficient just because they don't have 100 ladder games. Even if aren't actively playing ladder they talking about teambuilding and practicing battles against friends and team mates.
I just think using the given criteria you could miss out on potentially good candidates just because they don't see a benefit to playing ladder. Lifestyle pointed out that he would be a good example and I think most people would agree with that and honestly there are lots of good examples of outliers like this in every single tier. I agree that current TC members should be active in some form, I just don't believe that amount of ladder games should be the deciding factor about activity.
However I do like the idea of having separate TCs for each tier. And I would also be in favour of allowing more of the player base to vote. However I would prefer it to be an opt in system where reputable/knowledgeable players can write a short description of their accomplishments (which can include matchmaking) for the TC to then decide if they should be eligible or not. Instead of just amount of matchmaking games/win rate, I don't trust some guy who was given a pokepaste of a team to copy and spam for 100 games to have any influence over a tier and to not be biased.