While it's true that Virgin/FWC do have short distance revenue holes (e.g. Wigan to Warrington, Wilmslow to Stockport, Birmingham International to Coventry e.t.c), barriering comes at a huge cost and a potential inconvenience to longer distance travellers (which will be most passengers on First West Coast). Equally, barriers aren't good at checking fare restrictions, railcards and perhaps most importantly, advance tickets, which FWC will have many more of than other TOCs.
Installing barriers at Preston, for example, will I strongly suspect do more to protect Northern and TPEs revenue, who serve most of the local users. Indeed, Northern will be happy, as they currently pay for up to 3 G4S Inspectors to guard the platforms they most regularly use.
Warrington would certainly please ATW and Northern, again they operate services from nearby stations. I could go on and on...
Remember FWC isn't FGW, shorter distance commuters are very much in the minority. Most FWC stations have other TOCs which supply the local services and they will be the winners from barriers..