So, I know this will come across as controversial, but I do not believe the Red Vardo Traders as a faction fits well in Port-a-Lucine, as someone who has played in the Port RVT on one of their PCs. It strikes me as odd that there is, essentially, a Barovian thieves guild that tries to operate in Port-a-Lucine. Among PCs and NPCs, the Red Vardo Traders branch has a known reputation for being thugs, thieves and killers and there are even IC books written and easily obtainable from the loot tables.
In Vallaki and Barovia, the Red Vardo Traders can act without impunity because there is no need for them to be discrete or "unthuggish" with exception to guidelines in the Tigan's Code. If a PC talks trash to the Red Vardo (calling them thieves, murderers, ect.) in Barovia, they can give them the Don Corleone special. In Port, however, they struggle to exist as every PC and NPC even knows what the Red Vardo Traders have a reputation for, but they struggle to do anything about because both the Tigan's Code and the Port branch itself focuses on discretion and subtly far more than the Vallaki branch. In often cases, it feels like your hands are tied in Port-a-Lucine as an RVT and trying to do anything thuggish likely gets you kicked out of the branch (or worse).
Let's also address the crux of the issue, being the RVT in Port-a-Lucine has an unsalvageable reputation in Port. For as long as I've known the group in Port-a-Lucine, they have had an uphill battle between DM NPCs, PCs, and otherwise of trying to market themselves as anything but what they have become known for (assassinations, thievery, and mafioso plays). Maybe it's intended by design, but it certainly makes it a stale faction to be in after a while because you know that trying to attain legitimacy in Dementlieu as an RVT just won't happen. The RP becomes exclusionary by nature as well. Perhaps it depends on the player base currently involved as well as DM attention, but when I played my RVT PC he was worse off when he joined the RVT than when he didn't. It was to the point where people RP'd less with my PC after he put on the black and red than before he did, which is a shame as DM supported factions should enhance RP rather than detract from it.
I think a much better fit for the Dementlieu setting would be focusing on the Bellegarde Trading Consortium as a faction (I'll admit I have a horse in this race too, but even before I had a PC involved with the Bellegarde I thought this). It is a homebrew designed by Arawn, but it realistically fits the setting much more than a backwater thieves' guild does. Why does the RVT have a base in Port-a-Lucine at all? It makes little sense to me that a Barovian organization would have an office across the known world. The Bellegarde Trading Consortium is a Dementliuse based organization that operates within the setting of Port-a-Lucine much more seamlessly than a Barovian mafia—and while granted there is a Bellegarde office in Krofburg, a Dementlieuse organization is much richer and makes more sense when it exploits poor workers in Krofburg. Let alone the fact that there has been conflict between the RVT branches in the past, lest we forget the 2k bag turf wars taking place in Vallaki (it was a real thing).
Lastly, there is the issue of logs being shared between the two branches. To my understanding, there are no other factions in game that share boards and logbooks with one another. Without getting much into recent events, the Port branch and the Vallaki branch share forum access despite being worlds apart and it has even played a role in conflict and recent rule changes. Even during DM plots where DMs have said that PCs don't see the other branch's logs, that relies on player integrity rather than shutting down access. Alternatively to opening the Bellegarde up as an official faction, what we could do is just create a separate forum for each the Red Vardo Trader branches.