1. It is possible to use the lounge if you are a regular, loyal BA customer in possession of a Gold or Silver BAEC card.
2. Catering does vary modestly between World Traveller and World Traveller Plus. You get served first, priority choice of meals and also a proper glass for your wine.
While permitting lounge acces and further differentiating catering may indeed be a nice idea, such improvements would devalue the Business class cabin. You are paying significantly less to travel in a Premium Economy product.
If it doesn’t meet you needs, pay to fly business, or just upgrade using your miles (just 10,000 BA miles is enough for a one way upgrade to http://www.newclubworld.com from DXB-LHR, for instance).
A BA Gold Card member travelling WT+ between Nice and LA earns enough miles on the flights that their upgrade is *almost* free.