About the ancient weapons:
I've just been wondering about it ever since I started watching the anime again, beginning from the fish man island arc.
One of the themes, if not messages, of OP is to value your nakama and believe in them.
Now I'm sure more than me have noticed, that Luffy trashed about half of that big boat Noah, and noticed the message from joy boy about the promise to raise the ship to the surface. Shirahosi being poseidon, the one to use her power to help raise Noah.
Pluton being the ship of which Franky held the blueprints for, these being destroyed by himself. The blueprints which were supposed to be handed down from prominent shipwrights through generations, in case the real pluton was revived(meaning it's currently 'asleep').
Uranus we don't know about yet as far as I've understood it all.
Taking this all into consideration; wouldn't you say that the straw hats are making things hard on themselves? Meaning these weapons are potential threats if they're in the wrong hands.
I mean, they destroy potential help against these weapons, and I'm thinking Noah is one of those thing which will help, considering the cautiousness Neptune was ordered about it.
Taking this back to one of the themes that I mentioned, do you think they will be, as Franky suggested when he destroyed the blueprints, figure things out when confronted with the situations? In other words, believeing in their strenght??
It's just speculations on my part, but I'm sure someone else must've noticed! It's so exciting!! :D