I do pentest too like the OP (or like he says, because I find some stranges things he says, in particular I would like he tells me the name of systems he broke into during the OSCP exam he mentioned to have which is not for everyone..) and find this "method" strange on different levels, for example:
- as mentioned before, explain to your network that thousands of leads comes from a single IP (and be paid)
- 2.4 Ghz wifi signal will be destroyed by a pair of thick walls, also if you use a 24dbi antenna like one was linked in previous posts, and malls usually has more than a pair
- in 2017 90% of people uses 3/4g and doesn't even care if there is free wifi because the main mobile OS are not informing anymore (by default) if there are any free wifi
I personally think this is more a fantasy of the OP or an actual method which can really worked a decade ago, but today....no way
I hope OP will contradict me. Just my 2 cents
I would disagree about 3g / 4g and not using free WiFi, if you are in a tourist hot spot. But I am swaying towards OP fantasy on this. All sounds OK and plausible, till you start thinking about the obvious issues.