Tex pointed out one of the biggest issues with high level activity on faf - there just isn't a critical mass of 2.1k+ high level players where players can "hop in" and play ladder.
What that means is the barrier to playing ladder effectively becomes much higher, as you basically have to hope that one of the few people you can match with is online and playing ladder. Sometimes the windows when people are playing ladder just line up, and you get a ton of decent ladder games (Tagada/Blodir a year go, Mozy/Thomas a while ago, Swkoll/Tex now). However, that isn't always going to be the case, and it's very demotivating when your ladder buddy isn't playing when you want to play (for me personally, there's quite a vicious cycle as playing less makes me want to play less). The issue is the way ladder works right now is that most people in the 2.1k+ range have very, very few people that they can realistically match up with: their opponent must be 2k+ rated, in a similar timezone, and actually active on ladder. You can probably count on one hand the number of people that fit those criteria for a given top player.
What is the solution to getting more high level ladder activity? Get more top players. This may sound facetious, but I am listing this as a solution because it is the best solution to the issue. If there is a critical mass of top level players, to the point where your top player could just drop in and play a ladder game, at least during the active timezones, it would really fix this issue. Of course, this is perhaps just a pipe dream, since even just getting more players ≠ getting more top players, really, we need a lot more players + the next bracket of players needs to get a lot better.
What is a more realistic solution to getting more high level ladder activity? Give an option for players to increase their search range, so that they can at least find a game if both parties are willing. I think being able to find a game at all, rather than literally being unable to find a game through matchmaking, is the most crucial part of the solution, and this is a fix that does exactly that.
Implement a checkmark that asks "Would you like to increase your search range? It will increase your chance of getting a game but also increase the chance of getting an unbalanced game." that the user can tick or untick. If you tick it, you get reduced search range (e.g. +/- 300, or whatever is reasonable), and if you untick it, the search range can increase so you can match with people 400 or 500 points away.
The rating system should be able to handle the "imbalanced" matchups that result (e.g. if I face a 1400 as a 1900 on ladder, I would have a 95% chance to win, but get like 2 points or something from winning, -14 from drawing, and -30 from losing), and players who don't want to use this option can just not tick the box, so I don't see any reason this shouldn't be implemented.