Are we really arguing that letting Chaos continue to corrupt Waystones is better than letting elves run them?
I always thought that people supposedly having an irrational distaste for elves was a meme, but now I'm reconsidering...
Don't be daft. You know what will happen. Everyone can see it coming from a mile away. It's the same question that happens with the damn silver and wood, what do you think "Magic Super site-weapon" will do to it? It's the reason why Waystone knowledge is kept secret.
The question being asked, and some fool will ask it, every time, for Greed, for Intrigue, or just the stir the pot from outside, is the obvious one:
"But see, we fixed these here Waystones, why should the Elves get to keep them? They're our Waystones! And if you argue otherwise, you're a traitor to the Empire, Sigmar, or have been bewitched by the Elves! FOR THE EMPIRE!"
I'm sure negotiating that is possible. And except if the Eonir try to assassinate all participants, the know-how will be spread to the Dwarfs and Empire.
Your idea of Elves trying to invade the Empire looks very alarmist. They have a very low population and growth rate, they are unlikely to wish loosing a lot of their people in a war. Even the Asrai, who are even more powerful and aggressive than the Eonir never tried that. And that idea of an Elvish holy war is utterly ridiculous.
Now see, I don't doubt we'll learn something. I don't doubt we'll learn a lot.
But Elves man. From contracts to geas, to just "Each Waystone is a unique artifact and what works for Elven ones may not apply to dwarven ones nearly as well." There are all kinds of ways for there to be hidden hooks and traps when dealing with the Fey. Which is what Warhammer Wood ELves and their allies basically are.
Or to put it differently: Just because we learn stuff doesn't mean we'll leave the forest, us or the dwarves, or even be allowed to enter it in the first place, without strident secrecy Oaths/Geas being laid down. Because Faries. And hell, the Runesmiths would require a similar Oath to even start speaking about such stuff, even if they decided to share it, so why anyone would think that the Elves won't be taking their own precautions against their secrets slipping out is silly.
For dwarves, it would be as simple as making them take an Oath. No assassins required. What does it matter if their knowldge grows if they/we can almost never use it?
As for pop levels, oh yes, Elves have low pop levels. That's why they need the massive rivers of magic. You know who has the numbers?
The trees do. We power up a couple of Waystones and suddenly they can give a live rendition of the March of the Ents.