IMO Virgin had/has one of the best priority boarding set ups (at its owned gates) that I have seen. It is/was so sophisticated and yet so simple, because it was well though out.
At its most basic level, I think it delineates well between "purple lane" and "red carpet", to ensure both groups have a good embarkation experience. Red carpet passengers generally don't have lounge access, so they do their waiting at the gate area. Purple lane passengers generally have lounge access, so they do their waiting away from the gate. The whole flow of humans through the gate area then acknowledges that basic dichotomy.
It functions well to allow allow purple priority passengers to decide if they want to board first, at their leisure or last. It also allows for last minute laptop work at the benches for business travellers, regardless of their colour code. And comfort and easy access for those travelling in the cheap seats with mobility issues.
The problem Virgin faces in monetising priority boarding, is that their owned gates are not designed for red and purple to mix until they enter the aerobridge. If you are seated in the the red carpet gate area, you would have to backtrack through the gate lounge and make a trek around to the purple lane. Conversely, calling a subset of red carpet passengers before others, is hindered by the one way, bottleneck layout of the seat and queuing paths, designed with a more egalitarian "first at the gate, first to board" mentality - so it will be interesting to see what they may come up with.