Ok I did a short test, and it's definitely ECEx that gives the problem in my game!
With CP + other mods but
without ECEx activated, AI starts with Settler + 2x Warrior + Scout on Emperor difficulty:
However, with CP + other mods and
with ECExactivated, AI now starts with Settler + 3x Warrior but
no scout:
Gonna do a few more tests to check that this is not caused by conflict with another mod, it would be nice if someone else could try to check this also.
Update > I have a mod that I use that changes the tech tree, and when I turn that off, AI starts with a recon unit as intended. Apparently there is some conflict here which causes the issue.
Update 2 > Found the conflict! The mod changes which skills AI starts with, so they don't start with Trapping skill, and since this was PreReq tech for Great Scout - and mod is set up to have AI start with a Great Scout on Emperor level - this caused the conflict and gave them a warrior instead. Changing the PreReq tech for Great Scout to the same as Scout seems to fix this so AI now starts with a Great Scout. Gonna do a bit more playtesting.
Update 3 > Did some more playtesting. Works like a charm now. AI happily explores and aggressively forward-settles me like there was no tomorrow.