Yeah, I don't think anything other than opposite CN is feasible really. Certainly not for me, as the colours are really what I see when I look at a bad edge - red/orange on U/D (or F/B in E-slice) ... or white/yellow round the side. Certainly after thousands of EOLines it'll become instinctive. I would probably say the issue is just practice ... if you can spare the time, just do tonnes of EOLine and it'll come....but I can't yet tell if an edge is bad just by looking at it yet (If you get what I mean). I still can't see the entire Roux block everytime I inspect either, so maybe my inspection just sucks.
I guess being nonCN helps somewhat for ZZ. At least at first.
Ohyea and yes I'm from the UK - originally from teuchter-land, north of Inverness.