I...that's just not true, right? Like, if we had even one WMD we could have used it to win the....gah, never mind.
We don't
actually have seven WMDs that we can use on a moment's notice. We have, if I've kept track properly, one strong WMD we can set up in an afternoon, one strong WMD we can set up in less than a year, and one weak WMD we can set up in an afternoon (that Leaf can probably counter)
The weak WMD is skywalking up and dropping rocks from storage seals to bombard Leaf. It probably won't work because the ninjas will grab their own skywalkers and kill us.
The strong WMD that takes less than a year is Elemental Mastery. At level 40 or so it liquifies air, which means - effectively - a humongous torrent of liquid nitrogen that sucks in more air that turns into more liquid nitrogen so it's an unending stream of liquid nitrogen that lasts for
seven hours. Easily a city-killer. Unfortunately, grinding it up to level 40 will take months of effort, so we can't use it now.
The strong WMD that we can set up in an afternoon is the one and only Stacked Implosion Nuke. Implosion seals function by sealing up a ton of air, getting destroyed by the violent influx of air created by the vacuum, and then unsealing the air so it rushes out in an explosion. If you can protect the seal from getting destroyed by the vacuum, you can stack a bunch of prepped Implosion seals on top of each other and detonate them all at once for a pressure wave capped in size only by the number of seals we use. Given an afternoon I feel pretty confident we could build a bomb that could destroy Konoha.
Now don't get me wrong, we've come up with
tons of WMD ideas. Most of them don't work, however, or the rules got changed because they were too easy to discover so everyone would have it (looking at you substitution nukes), but these three the QMs have distinctly
not shot down, and their methods are obscure enough that we're quite plausibly the first to discover them.
As to why Jiraiya didn't use them... you know his complex about the Watchers killing anyone who uses a big enough bomb, or does anything too fancy with seals? It's probably that. He could probably guess that we had WMD ideas ready if he asked, so he probably didn't want to use them is all.