It is the EU's problem how to stop others leaving. If it is seen penalising a member, about to be ex-member, in order to achieve it's aim, I'm sure that would be immediately picked up by those who want their country to leave also, as the EU showing it's true colours, and how it was all the more reason to get out now while the going is good, before it's too late.
I do not see this as being a paramount driver to any deal made. Any deals are supposed to be a win/win situation not a take it or leave it situation. (Well unless your negotiation team was useless.) It would be a gross EU error if that was the path they chose.
"//Theresa May will now be the Country's second female PM. Are you happy with that ?// The first one didn't do too bad a job IMO."
The first did an absolutely abominable job IMO, except when dealing with the EU or recovering the Falkland issue."