I know the 3 area + 1 gunner per round per eligable area restricions; but there are only 4 gunner troops in the game, right? Does this mean that one side can recruit all of them and leave his opponent without gunners?
It doesn't make much sense to me...
In reality, one side (usually the French) will be defending its soil from invading English; if the French player can control enough areas for long enough he will amass enough VPs to win. So the English will be the ones recruiting gunners, because the French can often just declare siege and sit it out. Of course, it might make sense for the French to recruit those gunners, not to besiege the English but to reduce their besieging capabilities.
(Note: in the Hundred Years' War, this is pretty much what happened. The English won most of the pitched battles, but just as often found themselves facing a walled city or fortress with the French inside taunting them....)