Did you know, that you will get notified when your Sicilian opponent has researched First Crusade? There is a subtle white text that shows in the same column where you see what techs have been researched and what units you created. If the tech remains the same and will not get nerfed, meaning it still can spawn up to 50 units, why not play that notification once the tech is CLICKED, not when it’s effect is already in action? This way you could 1. prepare with more army production and 2. the sicilian player could mind game by cancelling the tech. Point 1 leads me to the second idea I had.
Give Serjeants the Eagle Warrior armor class. Right now Serjeants are pretty tanky but have no real counter. Every other infantry is either countered by archers or melee (huskarls). Serjeants are unique by not having an actual go-to counter. Because Sicilians resist 50% bonus damage, an elite Serjeant would receive an additional 4 damage from champions (usually +8 bonus vs eagles), making a Champion switch (or unique infantry) once you see the First Crusade notification viable. What are your thoughts? 
Elephants, SIege, Cav archers and militia line all counter serjeants.
First crusade is op as hell though.
I have no issue with a warning for First Crusade and also a warning for Flemish Militia, the game warns you when someone starts to build a wonder if wonder victory is enabled, both of these are indications of an imminent attempt to push to end the game that you cannot scout for - unless there is a way to obtain information about what they’re about to do some other way(Not involving watching the score to see a small dip when they spend resources on it) it should inform you prior to the tech finishing research - it’s a bit late if you find out after they’ve started moving the units towards you - this means you have to constantly be suspecting that either civ will rush you with 50+ units at any point in the game after reaching castle age/imp and forces you to build army composition against infantry in advance instead of what they’re actually using on you in the moment
This only applies if First Crusade is not nerfed, if it provides a smaller amount of units in the future they will need to have some element of surprise to make it effective
Sorry, I’m against of any kind of exterior help about what are your oponent doing…
I even think scores should be eliminate during the game… This is not an arcade…
Scouting, drop Outpost for all aover the map… Prepare for First crusade always just in case…
The problem is that outposts and scouting will not help you figure out when the Serjeants are coming, so the only option is to
This is not a good idea if they are fielding units that are not Serjeants to fight you with, your counter to cavalry/archers isn’t going to counter infantry UU, so you’re forced to either use a bad composition against their current units, or use a composition that is bad against their instant units - and you have insufficient time to change your composition after you can see the serjeants unless you’ve got Perfusion or 20 production buildings
Now if they’re spamming Serjeants already it isn’t a problem, but if they are spamming Serjeants in castle age I don’t think that’s a very good strategy for them to use
This isn’t a problem if you’re Franks or something since you’re going to pretty much flatten anything with cavalry anyway, but not all civs get great mileage out of spamming knights and have to use something else to be effective <2 minute warning still isn’t a lot of time, it would just let you start to train a different unit type, you would still need to have it pre-upgraded to get it out in time to deal with the serjeants
This is a great idea. As @Sscral pointed out, building a Wonder also provides an early warning. So, this mechanic is already established.
I think the problem is the OP of the UT, an exterior help it would be a patch. If the number of saerjent would be 5 per TC, we are talking of 25 units max… It is a power spike, but you can answer with some preventive actions like, stone walls, some support infantry (like when playing against mesos), defensive castles, whatever…
I completely agree, if they reduce the amount of Serjeants there is no need to create a warning
If it would be applied, then First crusade’s researching should be unstoppable once you click it
Crusade may need some nerf but sergeants need a cost reduction…
Ironically this bonus doesn’t help infantry as much as it does for say, cavalry or siege (Sicilian are supposed to be an infantry civ after all). Serjeants can be beaten by HC and drop like flies to jaguar, cataphracts and samurai despite this bonus 11