Why are you using the present and future tenses for something which is now past tense?. The withdrawal agreement exists, it is now history. The only game left is whether the UK Parliament accepts or rejects it. A few days AFTER the referendum,the EU leadership,who were stunned by the decision, made an internal decision that they would act as one.,for the purposes of the withdrawal agreement. ,So it was always going to be Barnier . The UK attempted on a number of occasions to fracture that unity..
In starting the talks about future trade deals, the individual EU countries do have different wants and desires, so the process is going to be tortured. If the UK accepts the agreement that has been agreed, they do have an indefinite period of time to remain close to the EU ,and perhaps ,(forlorn hope as it maybe), come to their senses. ,and seek to reapply for full membership.
The logic of your position is strained with the comment." This was always about trade". If it were then why would the UK have tried to turn it's back on its most lucrative market?. What Mrs Mays current dilemma is to finally recognise this and marry it to the " taking back of our borders and making our own laws " narrative.