Bringing this to our OOC discussion. Regulus is the master of hermetic legalese, I'm not. XD
And some of this relates more to how we (players) want the Order and Tribunals to function.
My understanding as a player: by not being part of a Tribunal we would lack the protection given to a covenant (because covenants are formaly defined within a Tribunal, with every Tribunal having it's own rules). We would be just a bunch of magi living together.
Thus, our charter would also not be valid, putting everyting formerly belonging to Leonardus under some risk (but not too high of a risk, because of a bunch of reasons).
Augustus Nero, mentor to Clusius and quesitor from Normandy will register our charter drectly within Magvillus, which should give us at least some legal recognition, but that can only take us so far.
If we do not join a Tribunal, any issues brought against us will be prosecuted at the accusers Tribunal (this is my reading of HoH:TL). Since we are bordering three Tribunals, we might see fire comming from every side, and no one will be on our side. Politically, it's a pretty unstable situation.
Otherwise, there should be no ramifications. Every magus needs to be member of a House, but there's no obligation to be member of a Tribunal AFAIK. No one is going to march us or something like that.
For the game, I believe this will change the kinds of stories we will be involved with. Postponing ur decision would make the first few years more focused on dealing with the crossfire between Tribunals and chosing a suitable place. If we decide now, we skip ahead to the stories leading to joining the chosen Tribunal (but would still experience some crossfire).
Augustus Nero's move grants us some degree of protection, so I think we could just stay silent for a while and pretend we don't exist. Maybe until the next Tribunal (1214)? This is a bit risky.
It might be easier to protect us if we manifest intent of joining a Tribunal (say, Rhine) in 1207, but only properly join a Tribunal (any Tribunal) in 1214. This is also risky. XD
That's the premisse of the saga, a covenant bordering 3 Tribunals, in an unstable situation. I don't think we can escape some risk.
I think @Arthur can complement on what direction he will drive us if we postpone the decision (or just fail to join any Tribunal at all).
Oh, there has been some talk in the past about joining the Lotharingean movement (support the recreation of the Lotharingean Tribunal, between Rhine and Normandy, in the next Grand Tribunal). I'm not personally found of the idea, but it's also a path we can take (albeit later, so we would still need to join a Tribunal now).