There seems to be some concern floating around the thread that Hekarti is going to use the shrines to suck up all the magic in the waystones and do... something with it.
From what we've observed in quest, every single Taalite holy place we've visited is built on top of a waystone. If King Taal the Hunter, Lord of the Forest, isn't abusing the waystones through His sites of worship, then I don't see why Hekarti would do the same.
I don't want Hekarti shrines around the Empire because I'm worried humans might start worshipping Her, and that's the sort of thing that rarely ends well, but I'm not seeing anything to fear directly from Hekarti Herself.
I think people are looking too hard for the "gotcha" in this deal. Tindomiel have offered the resources, knowledge and expertise upfront without an immediate payment, and the only thing they want in exchange is the right to construct waystones (should we ever discover how) in a religious design of their choosing. They are essentially working for free, and their reward for this is... more work. If this design ends up being actively hostile towards the project, or the nations of the Old World, then we can confront them on that.
Remember that they are not asking for the right to build shrines where ever they want to without oversight or permission. They are asking to include a shrine with any waystone they are asked to build. A Buy-One-Get-One-Free type of deal. Do we want Hekarti shrines all over the world? Maybe not. But they are still limited in where and when they can build one, and if they lack the resources to do so we can ask another group to make it instead.
In fact, they are not even building the waystones. At least, not all of it. They will be "providing the Wind-based aspects of constructing Waystones". Dwarves can't do that. The Colleges might not be able to, due to their focus on mono-wind magics. That means it has to be an elf, and there's only 12 Grey Lords in existence, and eleven of them are busy on other things. If we're not getting the multi-wind expert from Tindomiel, then where are we getting it from?
So lets not assume they are planing on antagonising every faction they are in contact with. They hold just one council seat out of 20+. They want an alliance with the Empire. They want to be a part of the waystone project, and I believe they are negotiating in good faith here, and honestly, I think we need their connections and resources.