Given that, the first thing I expect to happen is some REAL BIG BAD APPLE that causes like half the cast to be washed away in favor of some contestants that people might exactly care about
Therein lies the rub. I don't think it'd matter who they brought on -- they'd all end up just like the ones who are already there. There's NOTHING for them to do to interest us. The soap opera element rots, there's no real physical interest (ala Survivor/Fear Factor/etc.), there's no plot. This is the show's premise:
"What if we get a bunch of single people together at a permanently open wet bar?"
Not exciting enough? Throw in some arbitrary 'rules' and make the contestants vote each other off so you don't have to worry about audience input. Blehh. Boooooooooooooring.
Now put the lot of them in the Brazilian rainforest with a survival kit and a pup tent and we're in business.
"Live every day as if it were your last, because one of these days, it will be."
- Jeremy Schwartz