A revolutionary group could be played with any of the House gangs, or the Ash nomads... think of what you're aiming for in terms of what they believe in and how they would fight.
Van Saar typically represent the technologically advanced and the factory owners due to their high tech usage. Personally that doesn't sound all that militia/revolutionary... I'd say more Orlock or Ash Waste depending on wether you want to stick to the house gangs, or stray out into the extra pdfs.
As an example, I've recently restarted Necromunda and have tried to represent a squad from my Imperial Guard/inducted miners army (see linky in footer) that have been dropped on Necromunda in their hunt for a heritek that destroyed their homeworld.
For me the Van Saar skill tree fitted as they are going to have access to tech knowledge and field aid thanks to their guard training as well as allowing them to all start with lasguns