Okay .. he it comes. Now my story comes from the fact that Muto magics sucked. But I'll tell you right now, this is no longer what that I think but still, it started with that.

If you look at wizard communion ( which still suck by the way ) it says that it is the great heritage of the Mercurian magic it allowed them to gather & cast great ritual spells ( if not all their spells ). In the Order, I find that the one's that are stupid enough to use it twilight much faster than the others & don't have any benefits except meaby a higher penetration score...

Now let us make our Mercurian heritage usefull. They were priest that used even mundane people in their communions. The rituals were probably some sort of prayor to a god like Mercury or Mars or any of the old payan gods.

They could bring back fertility to soiled grounds & call up a mighty storm & the stories say they even brought back the dead to life !

Bonisagus & his line were able to adapt much of this system & spells to work under the hermetic guidelines but I say that some were just too much entranched into mercurian magic to be fully intergrated. A few examples would be : Aeigis, Hermes Portal, etc.

These spells were part of a major discovery from mecurian magic to Hermetic since they do not obey the guidelines but can be cast using hermetic Techniques and forms. Using current rules, they are learned same as other spells but you can't modify the specs of them which I find is a poor ruling. I think that you can add much more to the historic backround & a lot more fun if you say that these spells had to retain the casting form of the mercurian magic. By that I mean that the spell is not learned, it is recited from a book ( a bit like a prayor ) You cast it same as if you know the spell but from the book only. Most Mercurian magics are high level(those that hermetic magic can't mimic easilly) & would require a wizard communion ( wow, would it be possible that Wizard communion has an utility once again !?! )

I think this adds flavor to the game...

I have always liked the idea of wizards being able to (and sometimes having to) cooperate to cast powerful spells, though I have never personally cared for the Wizard's Communion spell. It seemed to lack flavor in my eyes for magi to have to cast a spell, in order to cast a spell together.

I liked the Ceremonial Magic rules that were introduced in The Mysteries and have continued to use them in 5e. In the past, I have opted to use a variation of Wizard's Communion as an arcane ability, similar to Certamen, but it never got any play.

I have also always liked the idea of wizards having spellbooks and grimoires with spells that they can cast (via text) but don't necessarily have "learned". I was disappointed that 5e doesn't explicitly address casting from text. I do hope they reintroduce it in a future supplement, but til then, I continue to allow it circa 4th edition.