The real question is why was the WIFI disabled in the first place?
Even though you can, doesn't mean you should going online with CFW, if all the pre requisites has put in place to minimise system ban when going online, then you will be risking a 50/50 change getting banned.
Since we don't know any history of that switch because of it's current CFW state, the Switch could very well be banned or flag for banned once it goes online, hence the previous user disabled the WIFI option.
Has he contacted the seller to ask why the WIFI option is not there?