I’ve been playing around with various combinations of generic Crossbowman + Genoese Crossbowman against Knights a lot in the Scenario Editor. From what I’ve seen and considered, I believe Genoese Crossbowman are almost certainly only useful against cavalry when using them in a long term Feudal Age archer aggression strategy that continues into Castle Age and ends with a mixing in of Genoese Crossbowman. And I believe Genoese Crossbowman should be good enough at such a very specific strategy in a real game, that if they were buffed, then they would become broken.
For the details, I first made a test assuming both players spent an equal amount of time creating military. I did this by pretending the Italians player played Fast Castle into two Archery Range production with a Castle added later, and by pretending the generic Knight player played Fast Castle into two Stable production with a third Stable added later. I assumed the Knight player built 10 Knights out of each of the three Stables for a total army creation time of 900 seconds and total army count of 30 Knights. For the Italians player, applying the same total creation time over two Archery Ranges and one Castle produces 22 Crossbowman and 13 Genoese Crossbowman. Since the current amount of military buildings and units usually implies the game is in mid-late Castle Age, I also gave both armies full Castle Age upgrades except for Pavise. I then made the two armies fight. The results were disastrous for the Italians player, including when adding Pavise and starting the fight at maximum range. This made me think Genoese Crossbowman are not good for a Fast Castle strategy, where players going for the same Fast Castle strategy are likely to spend an equal enough time on creating military. I suppose you could play defensively to mass both Crossbow units, because long term adding more Archery Ranges and Castles is faster than adding more Stables due to both Crossbow units costing less total resources per minute than Knights. But that also means giving the Knight player a free boom.
From comparing same creation time armies I moved on to comparing same total resource cost armies. Using the same 30 Knight army from the last test comes to a total of 4,050 resources. Applying this same total resource cost for the Italians player between the two Archery Ranges and one Castle from the last test produces 38 Crossbowman and 15 Genoese Crossbowman. I gave the two armies the same upgrades from the last test and made the two armies fight. The Italians player, without Pavise and starting the fight at less than maximum range, still loses to Knights badly. Starting the fight without Pavise but at maximum range finally gave some promising results, where the Italians army has a 50/50 chance of winning that depends on how early the Genoese Crossbowman die. Last, starting the fight with Pavise at maximum range gives the best results possible, where the Italians army could consistently win against Knights with around 20% units remaining. For comparison, I tested 57 Crossbowman with Pavise against the same 30 Knights. The Knights stomped that normal Crossbowman army every time. It’s not even a close fight.
It’s clear to me Genoese Crossbowman has a place against cavalry in equal resource fights where Genoese Crossbowmen are not the entire army, but mixed in with normal Crossbows. But an equal resource archer army creates much, much slower than a Knight army. For example, the army sizes I used in the equal resource test comes out to 900 seconds for the Knight army vs. 1,356 seconds for the Archer army! A 456 seconds difference! This difference is why I said Genoese Crossbowman are almost certainly only useful in a long term strategy starting from Feudal Age archer aggression, where you have a head start in archer numbers over a Knight civ and might further delay Knight numbers with early economy damage with pressure continuing into Castle Age.
Using the same armies with Imperial Age upgrades, Cavalier, and especially Paladin, take the lead again by far. However, with a post-boom economy it should still be possible for the Italians player to fight back and win with even higher archer numbers. Because 3 Stable Knights cost 405 resources per minute, but 2 Archery Range and 1 Castle Crossbows cost 230 resources per minute, meaning the Italians player can add in more production buildings faster than the Knights player to keep the numbers advantage started way back in Feudal Age.
Next, and finally, I pretended Genoese Crossbowman got a cost and/or creation time buff, allowing me to add 2 more Genoese Crossbowman in the 30 Knights vs. 38 Crossbows/15 Genoese Crossbows matchup. The difference is HUGE! In the Castle Age, 13% more Genoese Crossbowman power is enough to win against Knights so hard, I don’t even need Pavise to consistently win! And with Pavise, the Italians army has so many units left over for raiding or more military fights, that it could be GG if the Knights player doesn’t scramble out Mangonels. The results would be no less than the same with a buff to combat stats. And with Genoese Crossbowman being better than generic foot archers since the release of DE, good luck using anything but siege or a stronger archer civ against an army of buffed Genoese Crossbowman and Pavise foot archers. This massive power spike from a relatively small boost, in addition to everything else I have said about combat performance, is why I said a buff to Genoese Crossbowman would make them broken. The safest buff I can think of, if there still needs to be a buff, is a cheaper and faster researching Pavise, as it’s a requirement for efficiently fighting heavy cavalry with Genoese Crossbowman even in the most ideal situation.
Other than that, my conclusion is the same as my opening.