We can't even make proper waystones without talking to Ulthuan or the Druchii. The nexuses are definitely going to be even more closely tied to the network, and we have no chance of somehow figuring out how to integrate a new nexus into the network without being told the proper commands. Theoretically we could develop our own entirely separate style of nexus, but that then runs into the problem of moving enormous amounts of winds and Dhar from one nexus system to the other. It's also a massive waste of time to reinvent the wheel.
I didn't say anything about connecting to the existing network without the proper commands. I do, in fact, expect us to need to collaborate with Ulthuan to hook up to their stuff*. It doesn't even
particularly rankle that we do, since while it's annoying that we can't when we're trying to make repairs that they're unwilling or unable to perform, it's understandable to be security-conscious about infrastructure like this.
I'm also not clear where the idea that we can't make proper Waystones without talking to Ulthuan or the Druchii comes from. We've made excellent progress on all components thus far, and while it's possible that the Foundation will prove more difficult, we haven't seen the results of that action to say one way or the other. Is this a matter of you defining a "proper" Waystone as either "one matching the Golden Age design employed by Ulthuan" or "one capable of connecting to the Ulthuan network"? Because if so I would firmly dispute that definition.
As for reinventing the wheel, that is exactly what we've been doing with the Waystones, thus far to great success. It's been noted that what was the best approach for the Golden Age alliance between Asur and Dawi may not be the best approach for modern producton and deployment of infrastructure that needs to be produced, repaired, and replaced in the modern day; I see no reason that wouldn't hold true for the development of a Nexus.
I also see very little reason that a system designed to absorb significant quantities of Winds and Dhar when they're in its vicinity and then shuttle them along would have trouble interfacing with a system designed to... Absorb and shuttle around significant quantities of Winds and Dhar to another point? We've seen on-screen that the existing network already has multiple types of Nexus, and we'd be examining existing ones as part of our research, so I don't see it being nearly as problematic as you seem to be implying it would be.
*(Although, if we were really, really, desperate and Ulthuan absolutely refused to negotiate with us, we wouldn't even need to interface "properly" with their network to get Winds and Dhar into it, as long as we were releasing the Winds and Dhar somewhere that existing Ulthuani infrastructure could pick them up. This isnt a good way to resolve that problem, but it is possible, and they can do literally nothing to stop us from doing it other than "invade and physically prevent us creating infrastructure to do so" or "cut off the flow of magic, because absorbing magic from the area is literally the entire point of a Waystone".)