If we go that route of diplo pressure for the price of having the Suez become an international zone; could we, uh, invite literally every power possible since anything happening to the Suez has global commerce implications in order to justify having our theoretical allies so far (Comintern, Arab League, Black Sea Pact) all there? Or is that a horrible idea.
From what the information posts tell us, inviting the Entente and the Christian League would not change the outcome, they are friendly with each other and Burgundy is more worried about the Communists than about the Reactionaries so most likely they would tell us that Macedonia is right and we should concede to all their demands, though, if we were to put Aragon and any Entente nation in the same room there would be a boxing match within seconds (noone seems to like Aragon).
Venice would want to complicate Macedonia's live in every way possible because of the betrayal but they are still palatable to other countries so they are the nearest thing we would get to a friendly country in such a conference but it seems to have a horrible relation with Italy, which is a part of the Entente.
It would be interesting to invate the American countries mostly because they are not interested in a 2nd World War so they would most likely try to appease both sides and that might sway Burgundy into a softer approach towards the issue given that they are trying to rebuild relations with their former colonies, though that might be dangerous becuase WW2 seems inevitable and if the americans were to be friendly with Burgundy that would mean that the Comintern has an out-of-reach enemy to deal with.
In summary, if we want a casus belli and some time to properly mobilize our army I would suggest inviting Aragon and anyone else that is not from the Christian League but if we geniunely want to create an international zone I would argue on only invinting the American countries (because they are mostly neutral hence they will care more about the profit than political considerations), Venice (to sway them towards us) and Macedonia (which is a given that is going to attend any such conference).
Inviting the Black Sea Pact or the Arab League would reduce the conference into a series of islamophobic slurs thrown by the Chriatian League answered by a series of equally christianophobic slurs (and anti-imperialist slogans) by the offended party which would be followed by a mutual declaration of war or something of the like (the europeans don't consider them equals and want to go to war agianst them so it would be kind of doomed into scalating to full out war).
Edit: I might be wrong about something so don't take my word as absolute, this are merely well informed theories.