So...your plan is for people who live in Mexico to apply for jobs currently held by illegal immigrants so that the companies are forced to fire the illegals and hire legals.
So...for every illegal you fire, one legal comes in and the illegal just shrugs his shoulders and goes home instead of trying to find other work here.
The employer who willingly hires illegals will of course post job offers to replace his illegal workers, and the employer who unknowingly hires illegals would do the same.
Riiiiiight...
There will have to be a "get tough on the employer" focus to any plan put forth in order for it to work.