One of the advantages to my mind of building a maximum functionality Waystone now is that if we build a second model it can be more different, so between them a greater amount of the 'solution space' is covered.
With this Waystone churning away being refined in the background doing everything the Golden Age version can do but better, we can then explore more innovative options.
I'll still my Wayboat proposal as an example. A Waystone built into a boat solves a very different use case to the one the Golden Age elder races were trying to solve, but one that is very useful in the modern day, particularly for Kislev. The simplest way of making it requires cutting a deal with a river spirit/god, but I think that's pretty manageable.
In general, an advantage of making a Jade riverine Waystone now is that it's leverage over river spirits. In future if we want to make a spirit dependent design they'll know they aren't the only game in town, that whatever they ask for has to be cheaper than the cost of the Jade method, otherwise we can just use that.
Similarly, a low production rate of Golden Age + Waystone for permanent installation could be supplanted by the temporary use of a much cheaper easier to make version that's not intended to last, so makes use of compromises that we don't want to make in the long term but are willing to in the short term.
Edit:
@Boney, I'm not sure if it makes sense, but would it be possible to build a Waystone that can work with three transmission methods, so it could work wi try the leylines, or a cooperative spirit, or with a river that's had the Jade's menhirs installed along its bed?