[X] Leave it to Regina, that is what she does best (Newborn Regent of Sanctuary)
You are just begging for Red Court sorcerers to use Chitchen Itza to funnel a fucking ritual curse down that convenient portal into Molly's magical biology. We are not the only people who know how to make superweapons. Or use them.
Dresdenverse ritual magic can be terrifying... as long as it has the right conceptual leverage. I'm not saying the portal couldn't ever be used as conduit for sympathetic magic, but then they would either need to bring the portal to Chichen Itza or Chichen Itza to it.
Otherwise it would be like the Red Court trying to use a sample of our hair for a curse in Chichen Itza, except that hair is in Chicago.
I know there are entropic curses that don't need a piece of you, but logically speaking that means they have
much higher power requirements (that would only increase with distance), and if Chichen Itza could function as a freely targetable intercontinental ballistic curse missile like that, then don't you think they would have used that against the White Council? Instead of needing to get a blood relative of Blackstaff?
Mab got hit in her own fucking capital city by someone swaggering up and slapping her with their magic dick when she wasnt expecting it. We are significantly less militarily and politically powerful than the Queen of Air and Darkness and her Court.
If you don't count Mother Winter, Mab herself and maybe also the forces tied to the Outer Gates, then I don't think that it's obvious at all, that Sanctuary's military is weaker than what's freely available for Winter to use. It's a postindustrial high tech military that has a lot of the weaknesses that the Earth's less developed equivalents have against magic removed.
You only need to remember what we encountered in Wicked City to see how dangerous such forces could be.
And the political power can't exactly be compared. We have
all the political power in Sanctuary. On Earth and especially Nevernever, we have much, much less than Mab, but, ironically, the portal itself now means we have more political power than ever before, which comes with increased potential for power projection. It would be a spectacularly bad idea, but we
could hypothetically have a go with Morgan's "Iceland scenario" now in South America and try to take it over.
Look, I'm not saying there aren't
real threats around, like Nemesis and Ethniu, or that we shouldn't close that portal when we can (we can always work to open one later again, under more controllable conditions), but you weaken your argument, if you try to overestimate every smaller threat and underestimate Sanctuary at the same time.