1) Not sure how we could the second. Sure he will go ham on infrastructure but compounding effects and all that.
2) Not sure why it would unnerve him. No more than Roswita getting the Gromril sword unnerved her. Besides, asking him to prioritize the development of the waystone infrastructure when he has all the other infrastructure to worry about is not really as small an ask as you seem to think it is.
If the Project reaches the point of studying nexus (which will surely be after the point of mass deployment of waystones), the Ice Witches aren't going to throw much of a fit about sharing how they made nexuses. It's easy to just have Zlata ask other Ice Witches for Nexus information. The Ice Witches like Mathilde, if they would rather Zlata not be the one handling the Nexus study they'll do it.
It would unnerve him because Kislev would be willing to pay massive amounts of treasure or diplomatic concessions to get more waystones. Just like every other order faction on the planet. Waystones would be some of the most valuable resources on the planet. Kislev would have been willing to build waystones under Tzar Vladimir. Boris is more than aware enough to know just how valuable waystones are.
If Mathilde had not succeeded, or had been found out, it would have seriously risked war between Kislev and the Empire. Mathilde had a lot to lose by agreeing. You are asking him to do something as payment for killing his father for something he would have eagerly have paid for. Do you see the dichotomy here?
If you're at the point where you're talking about dotting Bretonnia with brand-new Waystones you're not at the point where you need to do favours to bring them to the table, you're at the point where you decide what concessions you're going to wring out of them in exchange for permanently improving their entire country in literally every way.
We don't know they built the one at Alexandronov. We know the Castle was built so their network could have four points, but it's possible that was pre-existing network infrastructure, which they converted. It is also possible that they built a new Nexus but frankly I find it unlikely they're capable of building Nexuses but not the simpler Waystones, which the Project has yet to do. There's probably some other factor, that they can't replicate on a wide scale.
It's possible I suppose, that they (or just Teclis even) were willing to rebuild the Nexus, but only with substandard materials. Or that the Nexus at Praag was not actually destroyed, and so didn't require a monolith, just fixing up or re-routing again. Actually that makes me wonder if having the Network be god-based is in some ways a weakness? Like, if one of the gods' Nexuses are captured, they can be easily re-dedicated or something.
We know there was not a nexus at Alexandronov. There used to only be
three nexuses: Kislev City, Praag, and Erengrad. They explicitly raised Alexandronov to house the fourth nexus in Kislev's waystone network. They might have used materials they had to make the nexus, but that is still considerably more experience with building nexuses than anyone outside of Ulthuan or perhaps Araby* would have. Though it does seem to have been a long time ago, it is possible they lost the knowledge.
Teclis would not have had the resources on hand to restore the Praag nexus. I am also extremely skeptical of the idea that he would have been taught how. He was only a century old at the time, favored and brilliant yes. But that is not equivalent to being given insights into some of the most complex of Ulthuan's creations.
Ulthuan, as a nation, managed to rebuild a nexus at Fort Solace by using an Old One monolith. Teclis had no where near that kind of resources available to him. And as far as I am aware it seems that Praag was more affected by the Great War Against Chaos than Fort Solace. It still has streets weeping bloods.
*and Nehekhara, and Naggaroth, and Cathay
"That is why Castle Alexandronov was built. There used to be only three, the old cities of Norvard and Dorogo and Srebrograd, but if you have three and lose one it collapses. If you have four, you can lose one and fall back to the others and retake and rebuild later."
