If we're talking 1300, no; 1350+, yes. Battle of Crecy was 1346.
I suppose you could have a scenario where people basically set themselves up with an army of longbows, men-at-arms and all the rest a little early, but in terms of making a mod, you're going to run into some big issues:
1. Warband's Agent AI doesn't handle war bows like the real thing. AI troops simply aren't allowed to fire on high arcs like they did IRL, so their ranges aren't correct.
2. You'll need to handle all of the anti-cavalry obstacles that were used. Archers typically used sharpened stakes to make their positions difficult to assault. You can do that in Warband pretty easily and there are some code kits to do it and things like pavises, but the cavalry AI doesn't know what to do about that, at all.
It's not like it goes, "gee, they've planted stakes, let's form a shield wall and advance", or in the case of horse archers "let's circle outside the stakes and shoot them from the flanks and rear. The problems with this situation are really complex and there aren't any perfect solutions, I"m afraid.
Oh, and lastly gunpowder enters the scene around 1250, not 1350; the early firearms were actually really interesting but were mainly a fixture of siege warfare at first, due to both expense and the fact that the early ones were only accurate if they were on fixed mounts. It's not like firearms changed things overnight, though, and in 1350 they still weren't significant parts of field battles, although early field guns were starting to show up.
