I agree. I like to play with people with a higher rating,equal rating and lower rating.
Rating Range of Seeks

... I'm not able to get a guaranteed game against someone significantly stronger than me if I wish. ...
Try putting the desired rating range in the game title. Abort games and block players as necessary until someone in the range accepts.

That's obviously one workaround, but shouldn't it be much simpler?
Also, why block players? I was under the impression that a seek went into a pool of other seeks. If someone else seeks a game that matches the options in your seek, won't a game automatically start regardless of the game name? They don't have any control over who their opponent is.

That will only happen if you click in the little box that says "Automaticly start game when matching seek is found", or something alike.

That's obviously one workaround, but shouldn't it be much simpler?
Also, why block players? I was under the impression that a seek went into a pool of other seeks. If someone else seeks a game that matches the options in your seek, won't a game automatically start regardless of the game name? They don't have any control over who their opponent is.
Simpler, sure - Post here.
Blocking - It is the internet. You will have to block unacceptable players who insist on picking up the game.
Automatic Start - Advanced Settings / Uncheck "Automatically start my game if similar seek is found."
Not really sure if this is the best place to post this, but...
I'm curious as to why you can't seek games on Online Chess where your own rating is outside the rating range of your seek. This way, I'm not able to get a guaranteed game against someone significantly stronger than me if I wish. I don't see any problems with letting someone set a seek with whatever rating range they want. Since both players set a possible rating range for their opponents in open seeks, wouldn't a higher-rated player realize that he might be paired with a lower-rated player, and vice-versa?