Someone's going to settle Trelli shortly after they recover from the Horseman's Plague. Unlike Xohyr, there is a strong incentive to settle that particular spot. Still, I don't see any particular reason to rush. Trade and expansion are not the primary concerns of most civilizations right now, so Trelli's probably going to be mostly empty for a handful of turns.
On that note, the Khemetri have abandoned their northern colonies. If we're interested in Saffron Sea access, then it's going to be much easier to take and hold those than the straits; we'd have direct land access, and the Gul River would help negate the obvious infrastructure strain. Whether that'd be a good idea is entirely contingent upon how recovered we are and how well our subordinates behave, but unless the Khemetri recover unusually fast, it's likely to be our best option to get a port on the Saffron Sea for a while.
But that brings us into conflict with a peer power. That's even worse than Trelli.
Granted, we don't know what shape the Med and Khem is in. It's not been that long that rogue mercenaries rampaged through there and the disease will have led to even more refugees that turn to banditry to survive.