I hope you are right but I fear your confidence in her and her team might be misplaced. If so, this has direct relevance to Tesla stockholders. Weyand (and others) were happy to further politicize the Brexit talks "pour encourager les autres" that may consider also dropping out the EU in the future, as opposed to a good faith negotiation with a military ally and major economic partner. In short, to ensure there was economic pain for the UK in leaving the political project, whether this was necessary or not.
“We should be in the best negotiating position for the future relationship. This requires the customs union as the basis of the future relationship. They must align their rules but the EU will retain all the controls. They apply the same rules. The UK wants a lot more from the future relationship, so the EU retains its leverage.”
Whatever your view on the rights and wrongs of Brexit and the negotiating stances of both sides (and there is merit to the Commission’s stance if you support its goal of integration, expansion and federalism), the world and Tesla stockholders are in for a shock if Weyand and her colleagues adopt a similar negotiating stance in trade talks with Trump's White House, rather than making a genuine effort to reduce trade barriers for mutual beneficial interest.
Noting the personalities on both sides of the negotiation, my personal base case remains a period of US punishment tariffs on European autos with counterveiling tariffs form the EU. Let’s hope I’m wrong!