They can't 3bet often enough without being too exploitable themselves, that's their problem.
2bb is the more effective size for this so I'm going to use that as the example, the bigger the sizing the less effective this wide range is.
BTN and both blinds have 100bb, BTN bets 2bb, blinds have posted a combined total of 1.5bb, BTN needs to take the pot down uncontested about 60% to show a profit. Assuming we lose every single time we're contested. Remember if the blinds actually play back at us quite wide, we're going to play back fairly wide ourselves and are not going to lose all of these where we get contested, but since it's really hard to quantify (and I just suck at maths) I'm going to ignore that and assume we always lose.
So we need them to have an average VPIP in the blinds of less than 20 each. (!)
Ok, so ignoring how profitable that is. Wont raising ATC cause them to play back?... um, how? They're in the blinds, good blind defence is occasional 3bets and otherwise lying down and playing dead.
If they call, then we get a ton of
equity. Calling is obviously really bad vs a range that's so wide we've got to dump the vast majority of it to a 3bet.
If they 3bet then what sizing are they going to use? 3x? 4x? 5x+?
3x= BTN raises 2bb, SB folds, BB raises to 6bb, hero faced with a decision to call 4bb getting 2:1 pot
odds. SPR of 7.6 (after the call), IP. We're calling pretty wide here.
4x= BTN raises 2bb, SB folds, BB raises to 8bb, hero faced with a decision to call 6bb getting 1.8:1
pot odds. SPR 5.8, IP. Not as good as 3x but we still have a fairly wide calling range but villain is risking 33% more than when raising 3x and the only real additional problem caused for us is the SPR, but the increase in raise size gives us two advantages: first, he has to do it less frequently, second we can fold more often when he does 3bet.
Once we start going 5x and higher it turns into the same logic as why we never raise 5x+ anyway, we're risking too much for what we gain.
There's a whole bunch of complicated stuff when we take this post-flop, but in the interests of keeping this at a readable length, I'll just leave that subject with just: If you're unexploitable pre-flop you're making money from that position, just don't spew horribly post-flop, and you gain a lot of equity every time you're allowed to see a flop. FWIW, I think your cbet % should actually be really low just because your range is weak, but again, that takes some explaining.
There was a bit of a typo in one of my previous posts saying that the blinds can't defend profitably, well, they can if we ignore the amount of blinds they have to give up. They can get out of the way most of the time and 3bet occasionally and their without blind stat will be positive because we're folding a lot more than we're playing back but in order to do this they've got to give up a ton of blinds.
just waiting to see what FP says and then I'm ready. Or 15 mins, whichever comes first lol. 
