I think the idea of having villagers that can defend themselves would be a great idea. But i dont think all villagers should be able to. Perhaps have a new role (like blacksmiths and librarians etc.) like police or patrol something like that. who would be able to fight back against mobs but doing little damage until you drop then a sword or bow, but also unlike most mobs, have said swords and bows have limited durability so you have to come back and re-arm them. This would also be a great for people making mini games.
I assume your thoughts are a result of the recently revealed Village and Pillage update. I do agree, it would be nice to have some villagers help out in protecting themselves especially considering they are getting an AI overhaul, but as long as the Pillagers can't break blocks it should be fairly easy to defend a village.
Hopefully Iron Golems will be able to target the Pillagers. Perhaps we don't need a guard villager if the golems just did their job better because they are a bit slow and there are only a few of them.
Since 1.14 will add crossbows, why don't we arm the villagers with them? Iron Golems are slow, ineffective against hordes of zombies, hopeless against the new Pillagers, and often aren't even there. Villagers need to stand a chance against zombies/pillagers.