You would need to chop the cab off and redesign it from the ground up, it would be cheaper in the long term to order new trains. The cabs are notoriously cramped and visibility isn't all that great either in those units.
On top of route knowledge, the rules training that each guard receives is far more in depth than that of a platform dispatcher. We are talking about things like laying emergency protection, operating a train during degraded working, what to do when the Traction Interlock Switch or Emergency Bypass Switch as been isolated, correction method of communicating with the driver or signaller, making an emergency call, carrying out a controlled evacuation, how to react to an uncontrolled evacuation. The list is virtually endless and I haven't even touched base on traction knowledge (faults and failures, locking doors and carriages out of use) and PTS (vast majority of SWR's platform staff do -not- have this training) which is important for things like evacuations, isolation of the traction current (Emergerncy Switch Off as it's now known).
Not really sure how to take this comment, i think you will find that all grades have a healthy mix of age and gender, to assume that because they are younger and therefore less likely to be in a union and would be more inclined to break strikes by acting as contingency guards in the name of customer service is incredibly naive. I also take great offence at your assumption that as I as a guard treat my passengers as a 'inconvenience' when compared to other members of staff, they are my responsibility. It's my job to get them where they need to go as quickly, pleasantly and more importantly safely as possible. I treat all my passengers with dignity and respect (for which I expect it in return, no more no less) and I am more than happy assist in anyway than I am. I enjoy my job, it's the best job (in my opinion) on the whole railway and I want to continue doing that job. Most if not all guards I know share this view and to claim that guards are less professional and customer focused that 'younger' platform staff has no factual basis.
Oh and food for thought, in the last 20 years of the previous franchise the platform staff have had far more industrial disputes than the guards did.