I see three solutions to this, all of them problematic:
1) We put the ritual solely under the authority of WEB-MAT. Our Charter is specifically designed for stuff like this, but will probably mean having to properly employ Aksel as a member of WEB-MAT, rather than as a project collaborator. It would also mean that managing the deployment of the ritual would be our responsibility, and any political blowback would fall on us directly.
2) The Grey College publicly announces a partnership of some sort with the Cult of Haletha. This reinforces the idea that the Hedgewise are priests and therefore legal users of magic, but throws the College into conflict with Nordland and everyone who hates the Hedgewise, such as the Cult of Sigmar.
3) The Grey College establishes a "Forest of Shadows Branch College", probably under the authority of Kurtis. This is basically the same as option 1, but we're dumping the responsibility for managing the whole thing on someone else.
All three of these options mean either bending the Articles in some way, or subsuming the Hedgewise into the colleges and forcing them to obey the Articles or else (which is clearly something they don't want, or they would have done it already).
Edit: Oh wait, option 4) We pull a Deiter IV, and have Lutipold legalise the Nordlander Hedgewise, just like the College of Elementalists. I foresee absolutely no problems with this idea.