Throwing a note up here before I go to work, don't have enough time to elaborate on it, but I am going to try and cover this tomorrow morning-ish but I cannot make promises. I have a Dr.s appointment in the AM (test results and review, nothing serious and for those concerned, everything is going very well) and then a jaunt over to the inlaws.
Favelas should be graded, with something like a 1A graded area effectively being the same as living in the arco, and some 1A areas might actually be nicer than living in an arco, if the arco in question might be an older model, or have some inconvenient quirks.
On down the list through the middle pay grades
Down to the 5F grade favelas which are functionally urban warzones with little or no police presence, intermittent utilities, and prevailing poverty and a strong criminal element.
Would also likely need to toss in a grading system comparable for seacologies, and more importantly, the cesspits and hives of scum and villainy that are the geofronts