"May contain traces of" just means that it's produced in a factory that also handles the trace ingredient. I think it's pretty unlikely that the ingredient will actually end up in your food.
Even some specifically vegan foods have this on the label, so I think a lot of 'safe' foods would be ruled out if possible traces were considered.
The Vegan Safe label could work on 2 levels - helping vegans choose food quickly and easily, and also showing non-vegans how many options they would still have if they chose to become vegan. Most supermarket food contains traces of something, so the latter wouldn't really be effective if traces were excluded.
Vegans who want to avoid traces could just double check the label (still a lot easier than reading all of the ingredients.)
You you make a very valid point Lys. I know a lot of vegans do ignore the 'may contain traces', including on potato chips as an example, because of the minute possibility of there actually containing any traces of these products, whilst some vegans, like AC's comment above, believe that it this might defeat the purpose, of which point I can see as well. Whilst doing some research I found that the Vegan Society in the UK have their own logo but, after becoming more flexible on the above issue, ended up receiving a lot of flack. Essentially, this is why I have asked for feedback, to see what others think. Just reading both yours and AC's response, I can see that this is going to be a very divisive issue. In regarding to working on the 2 levels as you mention, this is pretty spot on of why I want the label - a way for vegans to idnetify products that are vegan safe, without having to read the ingredients, yet would not affect non-vegans.