Right now, Bangladesh needs wealth more than anything else. Once they have wealth, they can spend it on things like OSHA.
Western nations could incentivize this by not assessing fines for firms caught producing their products in unsafe factories (I assume a couple billion dollar fine would be more impactful to Apple than a scathing NY Times article).
Because they would have nowhere to move to.
First... China has a humongous work force, which solely on numbers no other country can compete with, you need whole continents to get the same mass of workforce.
Second, in comparison to the rest of the BRIC competitors - Chinese workforce is relatively homogenous, well educated and most importantly of all they have a work ethic (Brazil? Hahahahah).
Third, low price is not the sole reason why stuff is produced in China (Go read why Ipad production is never returning to the US according to Steve Jobs).
That's not true, the safety expenses should be mandated and everyone's prices will increase accordingly. Prices are set according to costs and in the developed world, safety is a required cost. It could happen overnight if the big customers actually required it. Imagine if Walmart suspended billions of dollars worth of contracts until safety standards were met.