The 7 Hour Battle

[gollum]

The gunpowder event is hardcoded as far as i know sharpshooter, however nothing prevents you to take out the dependency of the gunpowder buildings to the event and designate gunpowder units in any era you like. The building.prod is the file you are after; it can be edited either with as test or using the handy gnome editor.

Conversely you can make the crossbows dependent to gunpowder by either making the gunsmith their required building and leave it linked to gunpowder or by making the 2nd level bowyer dependent to the gunpowder event. However in that case make sure that factions who get bow units like the Bulgarian Brigands or the Turkomans, Futtuwas, Nizaris and the like can make these via another building.

If i were you i'd leave the crossbows as high units and make the arbalests late units as they litteraly dominate anything else in terms of firepower and even factions like the Byzantines or the Egyptians or the English that get decent bow units can drop them altogether for arbs.