I wonder if this is an appropriate time for militancy - there are plenty of staff on the "market" at the moment, and who is to stop LM setting up the services for DOO and doing a deal with Aslef for an extra couple of grand a year?
I did never understand though how so many routes out of London going north went DOO but the WCML locals never did - scanning briefly through the LSE map (let me know if I've missed anything), but the locals out of Paddington, Marylebone, DC Lines from Euston, St Pancras (Thameslink), Kings Cross, Liverpool Street. To be fair Fenchurch Street DOO was quite recent but other than that Euston (with the exception of the DC Lines) seems to be the odd one out. I don't know about the Southern 3rd Rail routes so can't comment.