It's not a perfect match for generic nomadism, but I doubt it's something that can't be adapted to if stakes are this high. Like, we might get a bunch of cool government-sanctionedcowtroutboys out of the deal.
The thing is, steppe nomads don't move because they like the lifestyle. They move because their herds eat the vegetation and if they stay in one place their herds and then they will starve, and they can only come back when the land has had the seasons (or years) to recover from their presence.
In Warhammer, the steppe nomads also need safety in numbers. Scattering the tiny penny pockets of men that can permanently live off a settled location in steppe across the land seems like an invitation for them to be eaten by roaming norscan/greenskin/skaven/beastmen raiders.
This makes our Waystones far less vulnerable to several really bad failure conditions. If the forces of chaos destroy all the waystones connecting the empire to Ulthuan by leyline, our Waystones could still function on a backup system. Redundancy is *very important* when dealing with things as critical as this. The Hedgewise method, as much as I love the bag of rocks, isnt the best because it needs upkeep - though I suppose if its just a backup system its not *as* crucial to lack upkeep... the spirit method would also work but I think "Jade Wizard" is easier to access/scale across the continent than "Hag Witch capable of negotiating with riverine spirits", and there is also the unpredictability of exactly what the spirits would demand for this service.
Note you don't need a Hag Witch to negotiate with a riverine spirit. Priests of a river god can negotiate with their god, and anyone can go and have a chat with a naiad.
Importantly, you only need to negotiate once for each river, while I think you need a Jade Wizard to go to the location of the Waystone to be installed and perform a ritual there as it's being installed. That's a much greater logistical burden than negotiating once with the river as a whole and then install Waystones along the length of it.
The Hedgewise and Jade riverine options have the unique disadvantage that they need a specialist spellcaster from a particular tradition on the ground in the possibly dangerous location the Waystone is being raised. The other options can seemingly be erected by anyone, with only the construction in central locations needing specialsits, which is much easier and less dangerous.