The benefits of achieving "greater flexibility" alone seem so small that a dispute of this magnitude far outweighs them, though! The guards at our place pretty much all sign pretty much everywhere, even the new ones - and that's a big route card. Trains are very rarely cancelled for the lack of a guard. It just doesn't make sense - like a hugely disruptive solution looking for a problem.
This is against the backdrop of the RSSB report referred to in my previous reply to you, where destaffing is a pretty consistent theme as well as confirmation that there's not really a lot to be saved (financially) by just 'downgrading' guards.
A substantial fine for trains operated without a second member of staff would be one way of making sure that TOCs make an effort, but this isn't something that's currently proposed as far as I know, and I don't know how it'd realistically be enforced either. The latter could also apply to "exceptional circumstances" clauses - how does a driver, on the platform with his train due out in a couple of minutes, know that the "exceptional circumstances" explanation being given to them by Control, for the lack of an OBS, is genuine? He has no way of knowing whether the named OBS from another depot (for example) went sick fifteen minutes earlier or whether they've been off sick for weeks and rosters just couldn't cover the turn.
Safety at the PTI is something that I'd expect ASLEF to be making lots of noise about in due course. The fight to come, for them, is more about protecting their members' interests in that respect. The RMT, ultimately, are trying to protect their members' jobs and the safety argument is (quite reasonably) a way of justifying their jobs rather than one that will directly impact on their members - if that makes sense.
And yes, I agree that the RMT make themselves look very silly sometimes!