That seems like a sensible idea em
but what would happen if someone immigrated here, got a job, house etc, then after three years suffered an accident?
When they are discharged from hospital (assuming your system would allow them access to health care rather than just leaving them lying injured on the street) but unfit for work, would you
a) step over them as they live and beg for food on the pavement?
b) have the ambulance crew stretcher them straight onto a plane back to where they came from?
c) have an expensive tribunal system to separate the 'deserving' cases from the rest; who would then be destined for a) or b)
Or have you thought through a different solution?