(I'm going to tag @Demian here as well since you both worked on similar proposals)
Jonathan's message already alluded to this, but I'd like to unequivocally state (although I am by no means the ultimate authority on anything) that I think it's not the right time to land globally scoped traits.
Despite the interest and apparent need for a feature, a pitch sometimes cannot proceed because there are major unanswered questions about integration with the current ecosystem of tools. I think that will be the case here with globally scoped traits; it's something that only an extended period of community discussion and iteration will be able to gradually untangle.
That being said, I'd encourage you to continue exploring the Swift Testing project and look for opportunities to contribute original pitches of your own. You can start more informally with shorter forum posts to feel out interest rather than researching and implementing everything up front.