On this, are you going to allow new fleet behavior to be modded in at some point? There is only so much that can realistically be done with the current available fleet assignments... 
Most likely, yeah - I'd like to make fleet AI fully moddable at some point.
Right now, though, there's already a great increase in flexibility. You can override the text that the fleet tooltip shows - both in a fleet-global way, and per-individual-assignment - and along with the ability to control fleet movement, that gets you most of the way there, if in a round-about way. You can also now attach scripts to fleets (and other SectorEntityTokens), which is how the assignments are being managed here in some cases. For example, there's n "patrol assignment AI" script attached to a patrol that waits to see when there's no current assignment - i.e. the last set of assignments ran out - and then figures out what the next set of assignments should be.
The small fleets act really finicky, frequently they will decide to make 180s or just spin in circles because there are too many fleets they are interacting with. What ends up happening is looking like a giant mosquito mating ball, also very annoying trying to catch a fleet even if they are significantly slower.
Perhaps cut down on "opportunistic" behavior so small fleets dont get chased around by large fleets causing them to fly around looking like fools.
I'll keep an eye out. Haven't been seeing this in vanilla, but haven't really been playtesting it beyond functional testing at this point.
Yay! Will you try anything yet to invert the (at the moment upside-down) difficulty curve? Trading should offer a great starting point to that end, shouldn't it?
It's a start, yeah, but I don't think the pieces are quite there to make the endgame more challenging. That's almost certainly going to take giving AI fleets skilled combat officers. I'm more looking at balancing out trade income vs combat income, which isn't quite the same as changing the curve, though that can't help but change somewhat anyway. Hopefully in a good direction, but this isn't a pass where I'm terribly worried about the curve, beyond it being playable.
